dv: Properly split decoder and encoder initialization
mpeg: Change ff_convert_matrix() to take an MpegEncContext parameter

This will come in handy during dsputil splitting.
Merge commit 'e63b818dbe6060b606ae10eb184859f8b97d2353'

* commit 'e63b818dbe6060b606ae10eb184859f8b97d2353':
  dv: Properly split decoder and encoder initialization

Conflicts:
	libavcodec/dv.c

Merged-by: Michael Niedermayer <michaelni@gmx.at>
Merge commit '5dd8c08fd5e4c04d7a08d8934f0098a8a4a35c28'

* commit '5dd8c08fd5e4c04d7a08d8934f0098a8a4a35c28':
  mpeg: Change ff_convert_matrix() to take an MpegEncContext parameter

Conflicts:
	libavcodec/mpegvideo.h

Merged-by: Michael Niedermayer <michaelni@gmx.at>
avcodec/vp8: Fix multiple ff_thread_finish_setup() calls

Fixes Ticket3725

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>