Merge remote-tracking branch 'qatar/master'

* qatar/master:
  log: Only include unistd.h if configure found it
  ape: create audio stream before reading tags.
  mov: make a length variable larger.
  image2: Add "start_number" private option to the demuxer
  image2: Add "start_number" private option to the muxer
  avconv: remove a forgotten debugging printf.
  avconv: use more descriptive names for hardcoded filters.
  avconv: remove redundant handling of async.
  doc/filters: fix typo.
  h264: use asm cabac reader under a generic condition

Conflicts:
	ffmpeg.c
	libavformat/img2dec.c
	libavformat/img2enc.c

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