For all encoders and all decoders except MPEG-4 the unquantize
functions to use don't change at all and therefore needn't be
kept in the context. So discard them after setting them;
for MPEG-4, the functions get assigned on a per-frame basis.
Decoders not using any unquantize functions (H.261, MPEG-1/2)
as well as decoders that only call ff_mpv_reconstruct_mb()
through error resilience (RV30/40, the VC-1 family) don't have
the remaining pointers set at all.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
This is in preparation for only keeping the actually used
unquantize functions in MpegEncContext.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
