This fixes the underlying problem of the DV crashings - within blender
code.
Problem was, that we tried to seek on decode errors. (Unintentionally,
curposition wasn't advanced in that case). That triggered a bug within
ffmpeg, that made blender crash. My workaround fix for 2.49 actually only
prevented the crash, but didn't stop ffmpeg from only decoding black frames
after that point...
(The patch also cleans up the color conversion a little bit, by using
PIX_FMT_RGBA (still need to find a way to make it work with video files
that actually *have* an alpha channel. At least, latest FFMPEG-SVN swscaler
has the ability to use alpha.)
Looks like we can remove extern/ffmpeg now...
d47e1fee32