Enhance the spellfix extension with the ability to specify a rowid when
inserting new rows.
Change a while-loop into a do-loop in sqlite3VdbeSerialPut() for a small
size reduction and performance improvement.
Get the sqlite3VdbeSerialGet() routine to run faster by avoiding the use
of local variables.
Handle the 4-byte integer case in the stackless routine.
Improve the performance and reduce the size of the sqlite3VdbeSerialGet()
routine by avoiding the use of stack.
Performance improvement in the printf() logic by avoiding unnecessary stack
pointer movement.
Split the sqlite3Error() routine into sqlite3Error() and
sqlite3ErrorWithMsg(), for a slight size reduction and performance increase.
Performance enhancement in sqlite3PutVarint().
Combine the pcacheAddToDirtyList() and pcacheRemoveFromDirtyList() routines
into a single pcacheManageDirtyList() routine.  The resulting binary code is
slightly faster and a few bytes smaller.
Performance enhancements in the b-tree mutex logic.
Factor the saveAllCursors() routine of btree.c into two separate routines,
for a noticable performance improvement.
Another performance tweak: Split the sqlite3BtreeCursorHasMoved() routine 
into two with the second routine named sqlite3BtreeCursorRestore().  The first
now only reports whether or not the cursor has moved and the second tries to
restore the cursor.  This allows the sqlite3VdbeCursorMoveto() routine to be
refactored to avoid stack pointer movements, for a noticable performance gain.