In the sqlite3_context object, keep a pointer to the result value rather
than storing the result value in the sqlite3_context object and using
memcpy() to move the value back into its register
after the function returns.  This runs faster and saves over 500 bytes
of code space.
When determining whether or not a partial index is usable, do not assume that the cursor number assigned to each table in the query is the same as its index in the FROM clause. Fix for ticket [98d973b8f5].
Add a missing ticket number to a comment in index7.test.
Add a VDBE synopsis comment for clarification.
Refactor the sqlite3PcacheFetch() routine into three separate routines,
which are significantly faster overall and about 100 bytes smaller in
size as well.