Merge commit '2ba68dd0'

* commit '2ba68dd0':
  lavf: remove unreliable timestamp guessing heuristic

Conflicts:
	libavformat/utils.c

Not merged, as the change breaks ABI by removing a field from the middle
of AVStream.
Also, if you have files that decode better or worse without this code please
open a ticket on trac. If the timestamp code turns out useless it of course
should be removed.
Merged-by: Michael Niedermayer <michaelni@gmx.at>