Added TestIssue118, updates #118

See merge request cznic/sqlite!48

updates #117

- Upgrade to SQLite 3.40.0: https://sqlite.org/releaselog/3_40_0.html
- Support linux/ppc64le

https://modern-c.appspot.com/-/builder/?importpath=modernc.org%2fsqlite

modernc.org/sqlite builder results
Import path        Builder       Time                            Commit	                                  OS	  Arch	  Result Version
modernc.org/sqlite pi64          2022-11-28 12:46:52 +0100 +0100 76945bb9 linux   arm64   PASS   go1.19.3
modernc.org/sqlite freebsd_arm64 2022-11-28 12:01:58 +0100 +0100 76945bb9 freebsd arm64   PASS   go1.19.2
modernc.org/sqlite pi400         2022-11-28 11:59:01 +0100 +0100 76945bb9 windows arm64   PASS   go1.19.3
modernc.org/sqlite riscv64       2022-11-28 07:25:11 +0100 +0100 76945bb9 linux   riscv64 PASS   go1.19.3
modernc.org/sqlite win64         2022-11-28 06:03:26 +0100 +0100 76945bb9 windows amd64   PASS   go1.19.3
modernc.org/sqlite s390x         2022-11-28 04:20:49 +0100 +0100 76945bb9 linux   s390x   FAIL   go1.19.3
modernc.org/sqlite freebsd_arm   2022-11-28 04:19:40 +0100 +0100 76945bb9 freebsd arm     FAIL   go1.19.2
modernc.org/sqlite pi32          2022-11-28 02:59:24 +0100 +0100 76945bb9 linux   arm     PASS   go1.19.3
modernc.org/sqlite netbsd_arm    2022-11-28 01:08:46 +0000 UTC   76945bb9 netbsd  arm     FAIL   go1.18.3
modernc.org/sqlite win32         2022-11-28 00:50:15 +0100 +0100 76945bb9 windows 386     FAIL   go1.19.3
modernc.org/sqlite netbsd_386    2022-11-28 00:02:35 +0100 +0100 41cc2963fceaf4e0c20bd592fc1e57936ff0b757 netbsd  386     FAIL   go1.18.3
modernc.org/sqlite nuc64         2022-11-27 20:45:49 +0100 +0100 76945bb9 linux   amd64   PASS   go1.19.3
modernc.org/sqlite ppc64le       2022-11-27 20:38:59 +0100 +0100 76945bb9 linux   ppc64le PASS   go1.19.3
modernc.org/sqlite darwin        2022-11-27 20:13:59 +0100 +0100 76945bb9 darwin  amd64   PASS   go1.19.3
modernc.org/sqlite freebsd64     2022-11-27 19:55:34 +0100 +0100 76945bb9 freebsd amd64   PASS   go1.19.3
modernc.org/sqlite e5-1650       2022-11-27 19:47:20 +0100 +0100 76945bb9 linux   386     PASS   go1.19.3
modernc.org/sqlite darwin-m1     2022-11-27 19:44:56 +0100 +0100 76945bb9 darwin  arm64   PASS   go1.19.3
modernc.org/sqlite openbsd64     2022-11-27 19:30:58 +0100 +0100 76945bb9 openbsd amd64   FAIL   go1.19.1
modernc.org/sqlite netbsd64      2022-11-27 19:27:14 +0100 +0100 76945bb9 netbsd  amd64   FAIL   go1.18.3
modernc.org/sqlite openbsd_arm64 2022-10-25 09:34:13 +0200 +0200 e8e7bc00 openbsd arm64   FAIL   go1.19.1
modernc.org/sqlite freebsd-386   2022-09-18 01:02:00 +0200 +0200 99d11133 freebsd 386     FAIL   go1.19.1
All builder results
Results as of 2022-11-28 12:43:26 +0000 UTC

We can concoct any scheme we like for mapping
between uintptrs and mutexes.

Instead of using unsafe to map between actual pointers and uintptrs,
use a simple numbering scheme. Zero means nil. The next 12 ints
correspond to sqlite's 12 built-in mutexes. Everything after that
is an index into the mutex pool, appropriately shifted by 12.

This makes vet happy and makes the pointer checker happy.

It adds instructions and branches to the mutex acquisition path,
which is definitely unfortunate. In exchange, though,
we get simplicity, safety, and easy to reason about mutex "pointers".

This further simplifies the code.
It also removes a branch from the mutex lookup code,
at the code of adding bounds checks to the static mutex lookups.

lib: use less unsafe for mutexes

Closes #123

See merge request cznic/sqlite!49

A+C: add myself

Closes #124

See merge request cznic/sqlite!50

Only add the `beginMode`, set by `_txlock`, after BEGIN in non-readonly
transactions. Use the `ReadOnly` member of the `driver.TxOptions`
parameter to determine when and when not to add the `beginMode`.

sqlite: only add tx_lock begin directive for write txs

Closes #127

See merge request cznic/sqlite!52

Export Sqlite3_index* structs

Closes #134

See merge request cznic/sqlite!53