Merge remote-tracking branch 'qatar/master'

* qatar/master: (28 commits)
  mp3enc: write a xing frame containing number of frames in the file
  lavf: update AVStream.nb_frames when muxing.
  ffmpeg: remove unused variables from InputStream.
  doc: update ffmpeg -ar and -ac documentation to reflect reality.
  ffmpeg: remove pointless if (nb_input_files)
  ffmpeg: merge input_files_ts_offset into input_files.
  ffmpeg: merge input_codecs into input_streams.
  ffmpeg: drop AV prefixes from struct names.
  ffmpeg: deprecate loop_input and loop_output options
  gif: add loop private option.
  img2: add loop private option.
  AVOptions: in av_opt_find() don't return named constants unless unit is specified.
  x11grab: replace undocumented nomouse hackery with a private option.
  dict: extend documentation.
  lls: whitespace cosmetics
  docs: Use proper markup for a literal command line option
  docs: Remove a remark that isn't relevant any longer
  docs: Explain how to regenerate import libraries with MSVC tools
  docs: Mention that libraries for MSVC can be built with a cross compiler
  docs: Remove old docs that mention setting up a build environment with lib.exe
  ...

Conflicts:
	doc/ffmpeg.texi
	doc/general.texi
	ffmpeg.c
	libavcodec/Makefile
	libavcodec/dnxhddata.c
	libavformat/mp3enc.c
	libavformat/utils.c
	libavutil/Makefile
	tests/copycooker.sh

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