libs/gst/controller/gstcontroller.c: Fix refcounting here too, just like we did for _new_valist() a few days ago (#35...

Original commit message from CVS:
* libs/gst/controller/gstcontroller.c: (gst_controller_new_list):
Fix refcounting here too, just like we did for _new_valist() a few
days ago (#357180) (thanks to René Stadler). Also remove all those
'Since: 0.9' from the gtk-doc blobs.
* tests/check/libs/controller.c: (controller_refcount_new_list),
(gst_controller_suite):
Unit test for the above.