Fix some memory leaks in sceFont.

Which were highlighted quite well by tests.
Fix leaks in sceMpeg demuxing.
Fix some scePsmf leaks.
Correctly free a few FFmpeg resources.
Clean up some atrac/mp3 potential leaks.
Merge pull request #5771 from unknownbrackets/leaks

Stick a cork in some memory leaks
Fix memory leak in memory arenas on x64.
Oops, close the dir after listing it in ms0:/.

This was affecting some savedata modes, and showed up on tests.  Not sure
how it might've affected games, probably not much.