Merge commit 'd01e6841'

* commit 'd01e6841':
  mov: do not set avg_frame_rate in the demuxer

Conflicts:
	libavformat/mov.c

Not merged
The default fallback code that sets avg_frame_rate guesses the value
from a very small number of frames at the videos start and is wrong in
some cases for the file as a whole.
Now that makes it guess vs guess, but the code in mov is much faster

Also ideally the mov code should be fixed and give a exact avg_frame_rate
based on the actual cts from the index (CTTS/STTS)

If someone has sample(s) which show wrong fps values, please open a ticket
on trac or mail me if its private.
Merged-by: Michael Niedermayer <michaelni@gmx.at>