Merge commit '31931520df35a6f9606fe8293c8a39e2d1fabedf'

* commit '31931520df35a6f9606fe8293c8a39e2d1fabedf':
  mov: Do not allow updating the time scale after it has been set

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

diff --cc libavformat/mov.c
Simple merge