#37 Many plug-ins don't clean up after themselves

[Madd the Sane]

A lot of the import/export plug-ins don't clean up after themselves when they reach an error. I made the Mac-only APPL work because the code was similar to PlayerPROCore's code that loads MADK files; the code in the library does clean up after itself when it reaches an error.

See MADReadMAD in MainDriver.c or the APPL plug-in for what needs to be done.