codecs.conf: ffnuv can produce YV12 as format, so add it to list.

git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@37326 b3059339-0415-0410-9bf9-f77b7e298cf2
vo_null: set ACCEPT_STRIDE.

Besides better performance, this can avoid crashes since
without ACCEPT_STRIDE we might end up calling the unsupported
draw_frame function.

git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@37327 b3059339-0415-0410-9bf9-f77b7e298cf2
configure: Reject libvpx versions not supported by FFmpeg.

It needs VP8E_SET_MAX_INTRA_BITRATE_PCT, so test for it.

git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@37328 b3059339-0415-0410-9bf9-f77b7e298cf2