Simplify the accumulator reset for aggregate query processing so that it
uses a single multi-register OP_Null rather than a separate OP_Null for each
register.
Allow any arbitrary expression as the filename in an ATTACH statement,
including functions and subqueries.
Combine adjacent single-register OP_Copy instructions into a single
multi-register OP_Copy, where possible.  Fix the Synopsis comment for
multi-register OP_Copy instructions to show the correct register ranges.
Code simplification in sqlite3GenerateIndexKey() by making use of a subroutine
found over in expr.c.
Fix compiler harmless warnings in tclsqlite.c that appeared with GCC 4.8.x.
Add a case to speedtest1.c that demonstrates the need to factor OP_Column
operators out of inner loops.