Enhance (and fix) the MEMTYPE tags associated with heap memory allocations
when SQLITE_MEMDEBUG is used.
Restrict the scope of the valueToText() routine.
Fix the corruptI.test script so that it works with
SQLITE_ENABLE_OVERSIZE_CELL_CHECK and with SQLITE_DEFAULT_AUTOVACUUM=1.
Make sure the sqlite3VdbeMemClearAndResize() routine is never called with a
zero size parameter, since a size of zero could lead to either a memory leak
or an assertion fault.
More intuitive labels on ".wheretrace" output.
Fix the STAT4 range scan estimates for DESC indexes.