[Buildroot] new package: orc

Here's an updated patch-set that adds orc, the liboil runtime compiler.
This package replaces liboil functionality-wise, it's not a drop-in
replacement. Newer versions of gstreamer plug-ins require orc for
accelerated codepaths.

I've dropped some patches that added orc dependencies all over the
place. It should be sufficient to make gst-plugins-base depend on
orc (if it is selected). All other gst-plugins packages do already
depend on gst-plugins-base.