libavcodec doesn't allow multiple threads on some codecs, so blacklist them
to have only 1. Not sure if it would be easier just to revert few commits to
default whole to 1 thread.

I did't spot any other codecs that would exit if thread_count > 1 in libavcodec.

Fix #3613

add demux=avformat and play-and-pause, remove play-and-stop as it's
playlist-option not item. demux=avformat seems to help littlebit on
constant seeking (we don't want to dos as http-access closes and starts
new connection on seek currently ).

It closes #3512.

It is needed to be sure that the first image displayed after a discontinuity
(flush or seek) is the right one.

First priority is file-extension user gives, if that isn't
specified, use mux-value and if that's not valid (eg mp4), fallback
to flv-muxing.

Doesn't allow mp4-muxer on other than file-output (doesn't check rtp atm).
Also tries to be littlebit clever and cleanup sout-mrl.

Signed-off-by: Christophe Mutricy <xtophe@videolan.org>

Left-over from pre-libtool era

Basicly sets setting to empty or default. Shouldn't affect others than x264-module.

It is faster (and has use a bit of sse2), and better looking IMHO.

It segfaults otherwise.

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

It closes #3620.

Untested