APC SyncTERM:C;S;<fname>;<b64> ST
- Creates a file named <fname> in the cache directory and saves the decoded
  <b64> binary data in it.

APC SyncTERM:C;L[;<mask>] ST
- Returns a list of files in the cache directory with their MD5 checksums.
  Return value is in the format:
  APC SyncTERM:C;L\n<entries> ST
  Where <entries> is a series of filename/MD5 pairs separated by tabs and
  terminated by newlines.  So if there was a single zero-byte file:
  APC SyncTERM:C;L\nZero\t201e201e201e201e201e201e201e201e\n ST

APC SyncTERM:C;SetFont;<slot>;<name> ST
- Sets font slot <slot> to contain the <name> font.

This may all get an overhaul in the near future, but likely wont.  This API
was mostly for image and audio data, not so much for fonts, but since font
stuff is already here, it's a simple way to test things.

This also brings up undefined behaviour when an active font is changed...
We likely need to do something about that now too.