Consider disabling double-quoted strings by default

As per https://www.sqlite.org/quirks.html#double_quoted_string_literals_are_accepted, you may want to consider having the default for modernc.org/sqlite to reject double-quoted string literals. There are two ways to do this:

1. Compile with -DSQLITE_DQS=0. This will change the behavior for any user of modernc.org/sqlite/lib.
2. Use sqlite3_db_config on connections created through modernc.org/sqlite. This preserves the behavior in modernc.org/sqlite/lib, but gives a better default experience for users of the database/sql driver.

I'm using sqlite3_db_config in zombiezen.com/go/sqlite: https://github.com/zombiezen/go-sqlite/commit/ed99db83671cdf65aeb34b1bcd490ba66d712e97