Merge commit '6fd91fa1'

* commit '6fd91fa1':
  h264: increase MAX_SLICES to 32

The available sample decodes correctly before, but the reporter of the bug
claims that this change reduces artifacts. This is thus merged
If someone has samples that decode differently depending in the MAX_SLICES
value, please open a ticket on trac.
Also this change should be reverted if it turns out that the artifacts
that where seen had a different cause

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