ve_lavc: simplify and support more colorspace formats.

git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@36439 b3059339-0415-0410-9bf9-f77b7e298cf2
muxer_lavf: partially support formats creating files own their own.

This works with e.g. image2, but is a bit messy since
using img%d.png results in mencoder itself creating
a file with exactly this name while lavf creates the
correctly numbered ones.

git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@36440 b3059339-0415-0410-9bf9-f77b7e298cf2
Quick hack to allow using ffmpeg's image2 demuxer.

git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@36441 b3059339-0415-0410-9bf9-f77b7e298cf2
Support ffmpeg://dummy:// in muxer_lavf.

git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@36442 b3059339-0415-0410-9bf9-f77b7e298cf2