Upstream update. Please sign off.

-Andy

Changes:

SQLite Release 3.7.8 On 2011 September 19 (3.7.8)

Orders of magnitude performance improvement for CREATE INDEX on very large tables.
Improved the windows VFS to better defend against interference from anti-virus software.
Improved query plan optimization when the DISTINCT keyword is present.
Allow more system calls to be overridden in the unix VFS - to provide better support for chromium sandboxes.
Increase the default size of a lookahead cache line from 100 to 128 bytes.
Enhancements to the test_quota.c module so that it can track preexisting files.
Bug fix: Virtual tables now handle IS NOT NULL constraints correctly.
Bug fixes: Correctly handle nested correlated subqueries used with indices in a WHERE clause.
SQLITE_SOURCE_ID: "2011-09-19 14:49:19 3e0da808d2f5b4d12046e05980ca04578f581177"
SHA1 for sqlite3.c: bfcd74a655636b592c5dba6d0d5729c0f8e3b4de