oldSrcScale() is now unified with scale(). Use enableSource(bool enable)
to switch functionality. Partial screen updates are also posible because
of this.
initialize() had its prototype changes although it is functionally the
same.
setSource() no longer has a type parameter, removing support for
multiple source surfaces. They weren't useful anyway.
useOldSrc() was renamed to useOldSource() to conform to the names of
other functions.
