Adjust comments to show that subquery flattening restriction (10) was
removed from the code back in 2005.  This is a comment change only.
Do not flatten aggregate subqueries that contain min() or max() functions
so that if the min()/max() are discarded by the outer query, they still
function and cause non-aggregate expression to be evaluated on the minimal
or maximal row.
Remove the EXPENSIVE_ASSERTS in pcache.c having to do with the pSynced field
of the Pcache object, as they are incorrect, as revealed by recent pcache
enhancements.
Avoid attempting to call the xFetch() method of an sqlite3_io_methods object with a version number less than 3.
Fix tool/showwal.c so that it handles WAL files that contain 64KiB pages.
Performance improvement to the sqlite3MemCompare() routine by factoring out
sqlite3BlobCompare().