ext/ffmpeg/: ffdeinterlace port to 0.10.

ext/ffmpeg/: ffdeinterlace port to 0.10.

Original commit message from CVS:
reviewed by: Edward Hervey  <edward@fluendo.com>
* ext/ffmpeg/Makefile.am:
* ext/ffmpeg/gstffmpeg.c: (plugin_init):
* ext/ffmpeg/gstffmpegdeinterlace.c:
(gst_ffmpegdeinterlace_base_init),
(gst_ffmpegdeinterlace_class_init),
(gst_ffmpegdeinterlace_sink_setcaps), (gst_ffmpegdeinterlace_init),
(gst_ffmpegdeinterlace_chain), (gst_ffmpegdeinterlace_register):
ffdeinterlace port to 0.10.
Could be made a subclass of GstBaseTransform later on...