Now "-c copy" works.
Update FATE files.
Demuxer only split file into packets, no data is trimmed.
Encoder & muxer currently expect completely another format
where muxer writes stuff like disposal method which should
be really encoder job.
With this patch muxer only modifies delay between two packets.
Codec copy need to have same behavior between demuxer and
muxer to work correctly.
Fixes#6640.
The encoder now doesn't produce any extra graphic control extension
block anymore. Only the image is encoded, and the muxer writing
its own GCE containing notably the timing information now includes the
optional palette transmitted through packet side data.
This commit avoid setting clashes between the two GCE, and reduce the
size of the generated file with pal8 output.
