[MPlayer-dev-eng] configure cruft

[Diego Biurrun]

I have started to clean up configure somewhat and stumbled over a couple
of unused things that appear to be leftovers from waaay back:

- vo_syncfb: It has been disabled for five years now.  Nobody appears to
  be missing it, it should be removed.

- scandir, ftello, fseeko are all unused, should be removed from osdep
  as well.

Am I missing something?

Diego