configure: use pkg-config for libx264
Merge commit '4321e507564b2d8a5dfc630f8d6fefba6fdc1e92'

* commit '4321e507564b2d8a5dfc630f8d6fefba6fdc1e92':
  configure: use pkg-config for libx264

Not merged as requested by carl
a patch to fix this has been posted by carl to ffmpeg-devel

Merged-by: Michael Niedermayer <michaelni@gmx.at>
libavcodec/wmv2: remove dead code

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