Revert "GRAPHICS: do not clear the internal state of IFFDecoder on loadStream()."

This reverts commit 92c1ff31d6d8d78e58caa4d123ceb0fea43a48ed.
GRAPHICS: do not reset the extra parameters of IFFDecoder on destroy().

The two properties that control pixel packing and the size of the
surface need to be preserved for loadStream() to work correctly.
They are now under complete responsibility of the client.