Merge pull request #2760 from aballier/ffmpeg_cleanups

External FFmpeg cleaning

diff --cc configure.in
Simple merge

diff --cc lib/DllAvUtil.h
Simple merge

diff --cc xbmc/cores/dvdplayer/DVDCodecs/Video/DVDVideoCodecFFmpeg.cpp
Simple merge

diff --cc xbmc/cores/dvdplayer/DVDCodecs/Video/VDPAU.cpp
Simple merge