tests/check/: Some small and basic unit tests for playbin; not very useful yet, but at least a start.

Original commit message from CVS:
* tests/check/Makefile.am:
* tests/check/elements/.cvsignore:
* tests/check/elements/playbin.c: (GST_START_TEST),
(gst_red_video_src_uri_get_type),
(gst_red_video_src_uri_get_protocols),
(gst_red_video_src_uri_get_uri), (gst_red_video_src_uri_set_uri),
(gst_red_video_src_uri_handler_init),
(gst_red_video_src_init_type), (gst_red_video_src_base_init),
(gst_red_video_src_create), (gst_red_video_src_class_init),
(gst_red_video_src_init), (plugin_init), (playbin_suite):
Some small and basic unit tests for playbin; not very useful yet,
but at least a start.