Merge remote-tracking branch 'qatar/master'

* qatar/master:
  lavf: make av_probe_input_buffer more robust

Conflicts:
	libavformat/utils.c

Not merged as it depends on previous buggy changes

See: e74cd2f4706f71da5e9205003c1d8263b54ed3fb
See: ececbedaMerged-by: Michael Niedermayer <michaelni@gmx.at>