fate: add mpeg4 tests for frame size changes
avformat/m4vdec: mark as possibly containing discontinuities

This will be needed for the resolution change mpeg4 test

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
Merge commit 'f29c226af0ecc34c417b646580a9acd7d8bbaf48'

* commit 'f29c226af0ecc34c417b646580a9acd7d8bbaf48':
  fate: add mpeg4 tests for frame size changes

Merged-by: Michael Niedermayer <michaelni@gmx.at>
tests/fate/mpeg4: fix samples path

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