VP layer progress

In the interest of promoting discussion, I'd like to open up my
in-progress VP code for public viewing. Keep in mind this is under
constant revision, and probably doesn't compile, and would earn me
crates full of cola if it were actually used in some sort of release.
:))))

http://brightrain.aerifal.cx/~dalias/vp-in-progress/

I would recommend looking mainly at the API docs, vp.h, vf_pullup.c
(essentially finished), and vd_ffmpeg.c (almost finished). If you're
interested in the internals, you could look at vp.c too. The vo2
wrapper is mostly incomplete, and might change completely anyway.

Please send comments (or questions, if you don't understand) to the
list. Naturally the code by itself doesn't tell you what you can _do_
with it.

Rich