h263dec: call get_format() on resolution changes

Fail safe if the pixel format changes.
Merge commit 'c80a816142699dea9cf9fa66689a7838a487ed7e'

* commit 'c80a816142699dea9cf9fa66689a7838a487ed7e':
  h263dec: call get_format() on resolution changes

Merged-by: Michael Niedermayer <michaelni@gmx.at>
avcodec/aacdec: print element types when debug startcode is set

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