configure: drop X11 support

Disable all X11 related options.
configure: drop DirectFB support

Delete DirectFB option.
cleanup: delete OSS code

Delete dead OSS code.
cleanup: delete X11 code

Delete dead X11 code.
cleanup: delete DirectFB code

Delete dead DirectFB code.
cleanup: drop OpenGL code

Drop OpenGL code.
cleanup: delete some Mac OS X related code

Delete some Mac OS X related code.
cleanup: delete some unneeded audio outputs

Delete some unneeded audio outputs.
cleanup: delete some unneeded video outputs

Delete some unneeded video outputs.
cleanup: drop debian and rpm files

Drop some unneeded packaging files.
video: make FBDEV non-optional

Make FBDEV non-optional.
audio: make ALSA non-optional

Make ALSA non-optional.
audio: delete ao_pcm

Delete unneeded PCM audio output driver.
audio_out: minor cleanup

Do some minor cleanup.
dvd libraries: make dvdread & dvdnav non-optional

Make dvdread & dvdnav libraries non-optional.
configure: hardcode FFmpeg dependency

Just hardcode the FFmpeg dependency and make the build fail if not
present.
configure: hardcode a52 dependency

Just hardcode the a52 dependency and make the build fail if not present.