contrib: speex: fix build with recent automake

Disable the API function returning version string as it uses old
automake functionality that might be buggy/not supported anymore.
Don't bother fixing properly as we don't use that function and libspeex is now
an abandoned projet (move to Opus!)
avformat: set bits per pixel for video codecs

Fix decoding of MSRLE samples with avformat demuxer
avcodec: transmit palette to libavcodec >= 54
avcommon: Move the libavutil check where it belongs

Unbreak avformat-only builds.

Signed-off-by: Rafaël Carré <funman@videolan.org>