Add API to sqlite3_serialize/deserialize and sqlite3_backup_*

See merge request cznic/sqlite!56

=== RUN   TestIssue152
=== RUN   TestIssue152/SELECT_1_WHERE_false
=== RUN   TestIssue152/--_just_a_comment
    all_test.go:3019: sql: no Rows available
--- FAIL: TestIssue152 (0.00s)
    --- PASS: TestIssue152/SELECT_1_WHERE_false (0.00s)
    --- FAIL: TestIssue152/--_just_a_comment (0.00s)
panic: runtime error: invalid memory address or nil pointer dereference [recovered]
	panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x18 pc=0x5b5c69]

goroutine 9 [running]:
testing.tRunner.func1.2({0xaeff40, 0x13d9870})
	/usr/local/go/src/testing/testing.go:1526 +0x24e
testing.tRunner.func1()
	/usr/local/go/src/testing/testing.go:1529 +0x39f
panic({0xaeff40, 0x13d9870})
	/usr/local/go/src/runtime/panic.go:884 +0x213
database/sql.(*Rows).close.func1()
	/usr/local/go/src/database/sql/sql.go:3287 +0x29
database/sql.withLock({0xf82190, 0xc0001be990}, 0xc0001fbca0)
	/usr/local/go/src/database/sql/sql.go:3405 +0x8c
database/sql.(*Rows).close(0xc000133480, {0x0, 0x0})
	/usr/local/go/src/database/sql/sql.go:3286 +0x16d
database/sql.(*Rows).Close(0x4f12c6?)
	/usr/local/go/src/database/sql/sql.go:3270 +0x1d
runtime.Goexit()
	/usr/local/go/src/runtime/panic.go:522 +0x177
testing.(*common).FailNow(0xc000135040)
	/usr/local/go/src/testing/testing.go:980 +0x4c
testing.(*common).Fatal(0xc000135040, {0xc0001fbf18?, 0xc00001a0f0?, 0xb34fee?})
	/usr/local/go/src/testing/testing.go:1057 +0x58
modernc.org/sqlite.testIssue152(0xc000135040, {0xb34fee, 0x11})
	/home/jnml/src/modernc.org/sqlite/all_test.go:3019 +0x1d0
modernc.org/sqlite.TestIssue152.func1(0x0?)
	/home/jnml/src/modernc.org/sqlite/all_test.go:2998 +0x25
testing.tRunner(0xc000135040, 0xc0000638a0)
	/usr/local/go/src/testing/testing.go:1576 +0x10b
created by testing.(*T).Run
	/usr/local/go/src/testing/testing.go:1629 +0x3ea
exit status 2
FAIL	modernc.org/sqlite	0.008s

test binary compiled for linux/amd64
=== RUN   TestIssue153
=== RUN   TestIssue153/SELECT_1_WHERE_false
=== RUN   TestIssue153/--_just_a_comment
=== RUN   TestIssue153/#00
--- PASS: TestIssue153 (0.00s)
    --- PASS: TestIssue153/SELECT_1_WHERE_false (0.00s)
    --- PASS: TestIssue153/--_just_a_comment (0.00s)
    --- PASS: TestIssue153/#00 (0.00s)
PASS
ok  	modernc.org/sqlite	0.029s

From the issue:

> This issue might be related to this one: #152 (closed)

Confirmed.

Previously ColumnTypeScanType returned the reflect.Type of [][]byte
for BLOB columns, resulting in a failure to scan when the type was
constructed dynamically based on this return.

Update CONTRIBUTORS as requested

See merge request !60

Update sqlite.go's docs for Driver.Open()

See merge request !59

Implements `RegisterCollationUtf8` and `MustRegisterCollationUtf8`

Fixes #163

See merge request !61

Add capi_linux_ppc64le.go to fix ppc64le build

See merge request cznic/sqlite!62

Add connection hook

See merge request cznic/sqlite!63

Passing an already canceled/expired context to QueryContext/ExecContext
would return empty results without error because interruptOnDone would
immediately set the "done" flag to one so the calling function (query or
exec) would not enter the for loop doing the meaningful work.

Similarly, if the context is expired/canceled at the "wrong time", the
same behavior could happen.

This patch first check the context is still valid when entering the
function (before launching interruptOnDone), then if the funxtion is
about to return no values and no error, it checks if the "done" flag is
set and return the context error if it makes sense.

Handle context expired/canceled in Query/ExecContext

See merge request !65

While the query had succeeded, the context can expire right after. In
this situation, iterating the rows will fail. The test need to check for
sql.Rows.Err() too.

Also, don't forget to close sql.Rows when done to avoid memory leak.

fix error handling in test "QueryContext with context expiring"

See merge request !66

[bugfix] ensure statement pointers finalized

Closes #178

See merge request !67

docs(README): add `database is locked` error to new "troubleshooting" section

See merge request cznic/sqlite!69

feat: 89: Add Backup.Commit method

See merge request !70

TIL that 'go get example.com/foo' downloads only what the respective
package requires, but 'go mod tidy' will also download test-only
dependencies.

If needed, the CGo dependencies can be revived in a separate
repository/module. For now just delete it.

h/t: Dan Kortschak

use passed context in BeginTx

See merge request cznic/sqlite!71

Add support for setting SQLITE_FCNTL_PERSIST_WAL

See merge request !72

Implement ResetSession and IsValid methods in connection

See merge request cznic/sqlite!74