libs/gst/base/gstbasesrc.c: Make _wait_playing() not check any variables so that...

libs/gst/base/gstbasesrc.c: Make _wait_playing() not check any variables so that we can call this function from subcl...

Original commit message from CVS:
* libs/gst/base/gstbasesrc.c: (gst_base_src_wait_playing),
(gst_base_src_perform_seek), (gst_base_src_get_range),
(gst_base_src_set_playing), (gst_base_src_change_state):
Make _wait_playing() not check any variables so that we can call this
function from subclasses. Move the checks elsewhere similar to
_wait_preroll() in basesink.
Add some debugging.
Only signal the LIVE cond when we are going back to PLAYING.