gst/autoplug/gstspider.c: don't ref the element, adding already reffed it. And we...

gst/autoplug/gstspider.c: don't ref the element, adding already reffed it. And we didn't unref it later anyway... (hu...

Original commit message from CVS:
* gst/autoplug/gstspider.c: (gst_spider_link_add):
don't ref the element, adding already reffed it. And we didn't unref
it later anyway... (huge memleak when you used many spider elements)
* gst/gstelement.c: (gst_element_base_class_finalize):
* gst/gstelementfactory.c: (gst_element_factory_cleanup),
(gst_element_register):
* gst/gsturi.c: (gst_element_make_from_uri):
use gst_object_(un)ref instead of g_object(un)ref