Merge commit 'c1868e7e'

* commit 'c1868e7e':
  lavf: simplify handling of offset in av_probe_input_buuffer()

Conflicts:
	libavformat/utils.c

The simplification is broken and does not work at least for ffmpeg,
thus this change is not merged.
Merged-by: Michael Niedermayer <michaelni@gmx.at>