Original commit message from CVS:
* gst/videotestsrc/gstvideotestsrc.c:
(gst_video_test_src_class_init), (gst_video_test_src_init),
(gst_video_test_src_parse_caps), (gst_video_test_src_query),
(gst_video_test_src_do_seek), (gst_video_test_src_is_seekable),
(gst_video_test_src_create):
* gst/videotestsrc/gstvideotestsrc.h:
Implement seeking in videotestsrc.
Small cleanups.