lavc/utils: fix metadata audio frame memleak in case of non refcounted frames.

The metadata must be set before saving the frame to avci->to_free,
otherwise it will leak.

Signed-off-by: Hendrik Leppkes <h.leppkes@gmail.com>
Signed-off-by: Clément Bœsch <ubitux@gmail.com>
avformat/avs: increase probe score to preempt conflict with avxsynth

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

Dynamically loads the library itself, rather than through VfW.
Supports AvxSynth on Linux and OS X.

Supports the new colorspaces added in AviSynth 2.6 when used
with AviSynth 2.6.
Provide local copies of AviSynth's and AvxSynth's requisite headers in compat/avisynth/.

The versions of the headers are the same as those provided with x264
for consistency's sake.