SQLite 3.7.15 -> 3.7.15.2 (bug fixes)

Upgrades bundled SQLite from 3.7.15 to 3.7.15.2.  This fixes a couple scary-looking bugs listed at http://www.sqlite.org/changes.html

I went ahead and did the version bump (to direct-sqlite 2.3.3.1) to make this easier to apply.