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 cznic/sqlite!72

Implement ResetSession and IsValid methods in connection

See merge request !74

updates #199, #200

This should finally unblock upgrading SQLite per se to latest release
once the builders are happy with this commit.

vendors libsqlite3@v1.8.0

write unit test for issue 209

See merge request cznic/sqlite!75

- doc.go: update SQLite version
- stmt.exec(): correct order of err assignment
- stmt.query(): do not finalite pstmt before it'll be used
- functionArguments(): do not copy from zero sized blob