Make the latm decoder less verbose on initialisation.

Reviewed-by: Paul B Mahol
Only skip MLP header in mpeg files if the codec actually is MLP.

Fixes PCM audio in Kansas Pheasant Hunt 2000 mpg file.
Reported-by: Mashiat Sarker Shakkhar
.gitignore: add /doc/examples/pc-uninstalled

Signed-off-by: Paul B Mahol <onemda@gmail.com>
Add a new function av_codec_get_tag2().

av_codec_get_tag() may return 0 both in case a codec_tag was
found and if no codec_tag was found.
The new function does not have this ambiguity.
Use new function av_codec_get_tag2() in ffmpeg.c.

Fixes ticket #1953.
mpegvideo: reset context state on failed thread update.

Fixes assertion failure

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>