Remove branch 'object_priority_queue_aka_z_mapping_surfaces'

Remove branch 'object_priority_queue_aka_z_mapping_surfaces'

This is really a merge, but with `ours' strategy, so that's really the
deletion of the branch. It wasn't a good design, so there's an another
rewrite, new_video with new_engine (with an another_new_font_engine),
and later new_audio and new_level_format, and somewhere i'll add support for
scripting through squirell, so there's a lot to do.

I've didn't removed this branch fully, because i think, some code shall
be usuable from this, because the problem is with the design (too
complicated, not extensible enough, ...), not with the implementation..