ext/ffmpeg/: various compiler fixes

ext/ffmpeg/: various compiler fixes

Original commit message from CVS:

* ext/ffmpeg/gstffmpeg.c:
* ext/ffmpeg/gstffmpegcodecmap.c: (gst_ffmpeg_codecid_to_caps):
* ext/ffmpeg/gstffmpegdec.c:
(gst_ffmpegdec_add_pixel_aspect_ratio), (gst_ffmpegdec_frame):
* ext/ffmpeg/gstffmpegprotocol.c: (gst_ffmpegdata_seek):
* ext/ffmpeg/gstffmpegscale.c: (gst_ffmpegscale_transform_caps),
(gst_ffmpegscale_handle_src_event):
various compiler fixes
* ext/ffmpeg/gstffmpegdemux.c: (gst_ffmpegdemux_src_event),
(my_safe_copy), (gst_ffmpegdemux_open),
(gst_ffmpegdemux_change_state):
actually return the result.  Tee hee.