Fix a problem in OP_IdxDelete as used by REPLACE conflict resolution that
comes up due to recent enhancements that reduce the work required for
UNIQUE NOT NULL indices.
Modify a HeapValidate assert in the Win32 native allocator.
Fix several harmless compiler warnings.
Convert several ALWAYS() macros in vdbe.c into assert() statements.
Fix issue with several memory allocation tests due to KeyInfo allocations now being shared.