avformat/matroskaenc: wrap V_QUICKTIME codec private in something that looks like its part of quicktime stsd

This is needed for matroska spec compliance
Fixes playback of SVQ3 in matroska with vlc
Fixes Ticket 3256

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit 8456bd2c0f3b08756f353646fe3b40a6772e665e)
avformat/matroskadec: support SVQ3 as generated by mkvtoolnix-6.6.0

Fixes part of Ticket3256

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit 5800b08572ef5f776950fc6f1b6572ba9a6b1933)

Conflicts:
	libavformat/matroskadec.c