Add a bit that tolerates 1/16 latency per frame in automatic frameskip mode.

Remove old automatic frameskip code.
Revert "Add a bit that tolerates 1/16 latency per frame in automatic frameskip mode."

This reverts commit d9b6322caafcbd355848a32acd8b8c0fa1746264.
Require auto_equivalent_skip to be greater than 0 before decrementing it if the code is drawing a frame early in automatic frame skip mode. Otherwise, overflow occurs, and we skip 4 billion images.