Use av_picture_copy() instead of libswscale to copy pictures. This removes the swscale dependency and is faster. Fixe...

Original commit message from CVS:
Patch by:
Hans de Goede <j dot w dot r degoede at hhs dot nl>
* configure.ac:
* ext/ffmpeg/gstffmpegcodecmap.c: (gst_ffmpeg_avpicture_fill):
* ext/ffmpeg/gstffmpegcodecmap.h:
* ext/ffmpeg/gstffmpegdec.c: (get_output_buffer):
* ext/ffmpeg/gstffmpegdemux.c: (gst_ffmpegdemux_loop):
* ext/ffmpeg/gstffmpegmux.c: (gst_ffmpegmux_collected):
Use av_picture_copy() instead of libswscale to copy pictures. This
removes the swscale dependency and is faster. Fixes bug #534390.