Adds expected const qualifier on 'buf' to match AVCodec.decode's declaration. Gets rid of another compiler warning
Adds expected const qualifier on 'buf' to match AVCodec.decode's declaration. Gets rid of another compiler warning

git-svn-id: a4d7c1866f8397a4106e0b57fc4fbf792bbdaaaf@16005 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

prajnashi/ffmpeg,prajnashi/ffmpeg,prajnashi/ffmpeg,prajnashi/ffmpeg