Merge remote-tracking branch 'qatar/master'

* qatar/master:
  os_support: Choose between direct.h and io.h using a configure check
  os_support: Include io.h instead of direct.h on mingw32ce
  x86: ac3dsp: Only refer to the ac3_downmix_sse symbol if it has been declared
  swscale: Remove two bogus asserts
  ac3: move ac3_downmix() from dsputil to ac3dsp
  lavr/audio_mix_matrix: acknowledge the existence of LFE2.
  mlp_parser: avoid mapping multiple disctinct TrueHD channels to the same Libav channel.
  lavu/audioconvert: add a second low frequency channel.

Conflicts:
	doc/APIchanges
	libavcodec/ac3dsp.c
	libavcodec/ac3dsp.h
	libavcodec/mlp_parser.c
	libavutil/audioconvert.c
	libavutil/version.h

Merged-by: Michael Niedermayer <michaelni@gmx.at>