Fix failing test. Newlines are not alowed in identifiers between guillemets.

See merge request cznic/ql!212

Implement delimited identifiers between guillemets.

Closes #210

See merge request cznic/ql!207

This allows key words and other formerly not allowed identifiers to be used.
Guillemets were chosen because all other string escapes were already used
in the grammar of QL.
Also implemented some unit tests.
Fixes issue #210

Implement the SQL standard COALESCE function.

Closes #211

See merge request cznic/ql!209

This function returns the first non-NULL argument, or NULL if all are NULL.
Argument count is unlimited.
Includes a test in testdata.ql.
Fixes #211.

To use the new format for newly created databases set the FileFormat field
in *Options passed to OpenFile to value 2 or use the driver named "ql2"
instead of "ql".

- Both the old and new driver will properly open and use, read and write the
  old (V1) or new file (V2) format of an existing database.

- V1 format has a record size limit of ~64 kB. V2 format record size limit
  is math.MaxInt32.

- V1 format uncommitted transaction size is limited by memory resources. V2
  format uncommitted transaction is limited by free disk space.

- A direct consequence of the previous is that small transactions perform
  better using V1 format and big transactions perform better using V2
  format.

benchmark                        old ns/op      new ns/op      delta
SelectOrderedFile1kBx1e4-4       1329006807     255517723      -80.77%
CrossJoinFile1e3NoX1e4-4         3107615747     619794528      -80.06%
CrossJoinFile1e4NoX1e3-4         3354802646     700357061      -79.12%
SelectOrderedFile1kBx1e3-4       123908159      26627421       -78.51%
CrossJoinFile1e2NoX1e3-4         27598600       6474143        -76.54%
CrossJoinFile1e3X1e4-4           335359531      78790606       -76.51%
SelectFile1kBx1e3-4              4562622        1092952        -76.05%
SelectBoolFileNoX1e3Perc5-4      1781983        517165         -70.98%
SelectBoolFileNoX1e3Perc50-4     1789031        519676         -70.95%
SelectBoolFileX1e4Perc5-4        1199502        359018         -70.07%
SelectFile1kBx1e4-4              40393899       12168884       -69.87%
SelectFile1kBx1e5-4              398938019      122302661      -69.34%
SelectBoolFileNoX1e4Perc50-4     17760045       5522018        -68.91%
SelectBoolFileX1e3Perc50-4       1050091        328726         -68.70%
SelectBoolFileNoX1e4Perc5-4      17723524       5808971        -67.22%
SelectBoolFileX1e4Perc50-4       10402097       3697792        -64.45%
InsertBoolFileX1e3-4             41825364       15918052       -61.94%
SelectOrderedFile1kBx1e2-4       9774335        4492106        -54.04%
CrossJoinFile1e3X1e2-4           1617783        785663         -51.44%
InsertBoolFileX1e1-4             4927433        9665456        +96.16%
InsertBoolFileNoX1e2-4           4638139        9045240        +95.02%
SelectBoolFileX1e3Perc5-4        61143          31704          -48.15%
InsertFile1kBn1e3t1e4-4          227403851      417962957      +83.80%
InsertBoolFileX1e2-4             5205319        9355281        +79.73%
SelectFile1kBx1e2-4              180977         101025         -44.18%
InsertFile1kBn1e0t1e2-4          493998605      882267286      +78.60%
CrossJoinFile1e2X1e3-4           1266888        711538         -43.84%
SelectBoolFileX1e2Perc5-4        9774           5497           -43.76%
CrossJoinFile1e3NoX1e2-4         11920217       6735563        -43.49%
CrossJoinFile1e2X1e1-4           32795          19315          -41.10%
InsertFile1kBn1e1t1e2-4          51884617       86750690       +67.20%
CrossJoinFile1e1X1e2-4           30959          18643          -39.78%
InsertBoolFileNoX1e1-4           4936511        8171014        +65.52%
CrossJoinFile1e4X1e3-4           138960718      88406050       -36.38%
InsertFile1kBn1e3t1e3-4          22921971       35507302       +54.91%
SelectBoolFileX1e1Perc5-4        5363           3477           -35.17%
SelectBoolFileX1e2Perc50-4       52708          34471          -34.60%
InsertFile1kBn1e1t1e3-4          513335347      775494042      +51.07%
InsertFile1kBn1e2t1e2-4          6725217        10065333       +49.67%
CrossJoinFile1e1NoX1e2-4         241349         162557         -32.65%
InsertFile1kBn1e2t1e4-4          834129466      1229457620     +47.39%
SelectBoolFileX1e1Perc50-4       10724          7279           -32.12%
InsertFile1kBn1e2t1e3-4          70257020       102477109      +45.86%
SelectBoolFileNoX1e1Perc5-4      9691           6647           -31.41%
CrossJoinFile1e2NoX1e1-4         178373         123161         -30.95%
SelectBoolFileNoX1e2Perc50-4     79529          55208          -30.58%
SelectBoolFileNoX1e1Perc50-4     9276           6542           -29.47%
InsertFile1kBn1e3t1e5-4          2581234930     3629377500     +40.61%
SelectBoolFileNoX1e2Perc5-4      82316          58945          -28.39%
InsertBoolFileNoX1e3-4           8478206        10126515       +19.44%

- V2 format uses substantially less memory.

benchmark                        old bytes     new bytes     delta
InsertFile1kBn1e3t1e3-4          4683629       214099        -95.43%
InsertFile1kBn1e3t1e4-4          42326873      2174786       -94.86%
InsertFile1kBn1e3t1e5-4          397886672     21182824      -94.68%
InsertFile1kBn1e2t1e3-4          4111234       221634        -94.61%
InsertFile1kBn1e2t1e4-4          40488844      2214520       -94.53%
InsertFile1kBn1e2t1e2-4          400895        22224         -94.46%
InsertFile1kBn1e1t1e3-4          5063280       411028        -91.88%
InsertFile1kBn1e1t1e2-4          498687        41186         -91.74%
InsertFile1kBn1e0t1e2-4          1571434       238228        -84.84%
SelectBoolFileX1e3Perc5-4        52729         10235         -80.59%
InsertBoolFileX1e1-4             33802         7251          -78.55%
SelectOrderedFile1kBx1e2-4       1486433       373721        -74.86%
SelectOrderedFile1kBx1e3-4       16538318      4318323       -73.89%
SelectBoolFileX1e2Perc5-4        7307          1944          -73.40%
SelectOrderedFile1kBx1e4-4       170936232     48409036      -71.68%
CrossJoinFile1e3X1e2-4           814207        255715        -68.59%
CrossJoinFile1e1X1e2-4           17059         5385          -68.43%
CrossJoinFile1e2X1e3-4           573394        191340        -66.63%
CrossJoinFile1e4X1e3-4           78447465      27922856      -64.41%
CrossJoinFile1e2X1e1-4           19173         6954          -63.73%
SelectFile1kBx1e3-4              3518328       1344859       -61.78%
SelectFile1kBx1e5-4              351685469     134437012     -61.77%
SelectFile1kBx1e4-4              35166002      13444622      -61.77%
SelectFile1kBx1e2-4              351753        134910        -61.65%
InsertBoolFileX1e3-4             2646597       1070045       -59.57%
InsertBoolFileX1e2-4             179300        86247         -51.90%
SelectBoolFileX1e3Perc50-4       220300        108229        -50.87%
InsertBoolFileNoX1e1-4           9348          4622          -50.56%
SelectBoolFileX1e2Perc50-4       22429         11300         -49.62%
SelectBoolFileX1e4Perc5-4        221089        113039        -48.87%
CrossJoinFile1e3X1e4-4           46730586      24064380      -48.50%
SelectBoolFileX1e1Perc5-4        2521          1360          -46.05%
SelectBoolFileX1e4Perc50-4       1929656       1055191       -45.32%
SelectBoolFileX1e1Perc50-4       4530          2600          -42.60%
SelectBoolFileNoX1e4Perc50-4     2403360       1521074       -36.71%
SelectBoolFileNoX1e4Perc5-4      2403349       1521074       -36.71%
SelectBoolFileNoX1e3Perc5-4      241282        153072        -36.56%
SelectBoolFileNoX1e3Perc50-4     241280        153072        -36.56%
CrossJoinFile1e2NoX1e3-4         2169344       1389074       -35.97%
CrossJoinFile1e3NoX1e4-4         241111128     154415488     -35.96%
CrossJoinFile1e4NoX1e3-4         278177376     178324552     -35.90%
CrossJoinFile1e3NoX1e2-4         2714091       1752226       -35.44%
SelectBoolFileNoX1e2Perc5-4      25076         16272         -35.11%
SelectBoolFileNoX1e2Perc50-4     25076         16272         -35.11%
CrossJoinFile1e1NoX1e2-4         57853         37680         -34.87%
CrossJoinFile1e2NoX1e1-4         52762         35472         -32.77%
SelectBoolFileNoX1e1Perc5-4      3472          2592          -25.35%
SelectBoolFileNoX1e1Perc50-4     3472          2592          -25.35%
InsertBoolFileNoX1e2-4           45394         39760         -12.41%
InsertBoolFileNoX1e3-4           423187        391102        -7.58%

	modified:   Makefile
	modified:   all_test.go
	modified:   doc.go
	modified:   driver.go
	modified:   driver/all_test.go
	modified:   driver/driver.go
	new file:   encode2.go
	modified:   etc.go
	modified:   file.go
	new file:   file2.go
	new file:   file2_test.go
	modified:   plan.go
	modified:   storage.go
	modified:   storage_test.go
	new file:   v2.sh

Fixes #205.

ql: add support for Go module

	modified:   all_test.go
	modified:   storage.go

	modified:   Makefile
	modified:   all_test.go
	modified:   driver1.8.go
	modified:   go1.8_test.go
	modified:   parser.go
	modified:   ql.y
	modified:   scanner.go
	modified:   scanner.l

issue190: add test to show argument order issue

Use physical columns instead of logical columns with simple indicies

The difference between physical and logical columns only appears after
dropping a column.

Fixing this uncovered another bug where dropped columns are returned
from selects with a WHERE clause using an index. That bug is from
dropped columns not being filtered out after reading a row. The
filtering is done in a simple table scan, that code is replicated in the
path used by index plans. This bug is also fixed.

Fixes #188

There is an invariant that simple index n+1 is for physical column n.
The difference between the physical column list and the logical column
list only appears when a column is dropped.

Fixes #187

Additionally some minor cleanups were made.

	modified:   all_test.go
	modified:   btree.go
	modified:   doc.go
	modified:   expr.go
	new file:   lexer.go
	modified:   mem.go
	modified:   parser_test.go
	modified:   plan.go
	modified:   ql.ebnf
	modified:   ql.go
	modified:   ql.y
	modified:   scanner.go
	modified:   scanner.l
	modified:   scanner_test.go
	modified:   testdata.log
	modified:   testdata.ql

Support blob type for lt,gt,le,ge,ne,eq operators using native bytes.Compare

Add NamedArg support

Read input from stdin

Fixes #178

Add sleep built in function

This function can be used to delay execution.

This is similar  to pg_sleep for postgresql. It takes a single argument representing a number in secods.

```
select sleep(5)
```

Will sleep for 5 secods.

Since dummy tables lack from bodies it is safe to return the selectDummyPlan as early as possible avoiding evaluating fields twice.

This will properly account for the sleep function.

`sleep(5)` is supposed to sleep for 5 seconds but if we dont return  the selectDummyPlan early  it will sleep for 10 seconds.

Evaluate field expression when selecting on dummy tables

This commit ensures the field expression is evaluated when selecting from nothing.

For instance you can

```
select 10, now();
```

This query will return a row of two values, 10 and `time.Time`.

This functionality is handy when we try to implement the pg_sleep function to slow down queries.

so we can do something like

```
select 1;select sleep(100);select 2;
 ```