Add a missing '#include "tcl.h"' to test_rtree.c.
Improve performance of sqlite3VdbeRecordCompare() by using an approximation
that might give false negatives and only running the more expensive exact 
subexpression if the approximation fails.
Factor all KeyInfo object allocations into a single function:
sqlite3KeyInfoAlloc().  Always allocate enough space so that 
sqlite3VdbeRecordCompare() can avoid checking boundaries and hence
run faster.
For the vtshim module, always zero out the xChildDestroy function pointer after calling it.
Performance optimization: Avoid calling convertCompoundSelecctToSubquery()
on queries that do not use the UNION, EXCEPT, or INTERSECT operators.
More than double the speed of the resolveP2Values() routine in vdbeaux.c by
moving from an extended if-else on every opcode to a switch.  Opcodes are
reordered in mkopcodesh.awk to put the switched opcodes close together,
for additional performance and to reduce code footprint.