Update ffmpeg to 2.8.8.

Adds HEVC, Opus, VC-1 and Vorbis to custom and minidlna profiles. This should
more closely match formats media being streamed on the local network via
DLNA/UPNP.

Removes raw aac, ac3 and h264 from minidlna profile. Most players expect
this content to come within a container (mkv, mov, mp4, mpegts, etc...),
so this was unnecessary for the profile's goals.

Remove libopus from being selected by the -custom's audio-dec profile, and as
a depend on -audio-dec. -audio-dec uses ffmpeg's internal Opus decoder, not
the external library.

Don't select specific parsers in libffmpeg-mini profile. The demuxers separate
streams from containers. Parsers break up the streams. These are not needed
for DLNA/UPNP. If a parser is needed, the ffmpeg configure script should grab
it.

Signed-off-by: Ian Leonard <antonlacon@gmail.com>