libopenjpegdec: return meaningful error codes
lavc: add error checking to apply_param_change.
oggparsetheora: K&R cosmetics, reformat

Also typedef the private data struct and make its name consistent with
the rest of Libav.

Signed-off-by: Vittorio Giovara <vittorio.giovara@gmail.com>
Signed-off-by: Anton Khirnov <anton@khirnov.net>
oggparsetheora: return meaningful error codes
oggparsetheora: check av_mallocz result