Before this, almost all module groups have been used for grouping functions
and fields in structures semantically. This causes them to not appear
properly in the file documentation and needlessly clutters up the "Modules"
index.
Additionally, this commit streamlines some spelling and appearances.
Call this new function before decode() to replace the custom and
inconsistant initialization in various decoders.
This function is equivalent to avcodec_get_frame_defaults() for AVFrame.
Signed-off-by: Aurelien Jacobs <aurel@gnuage.org>