Fixed in CVS

Hm, as I can see in current CVS, "sched" is unreferenced in
gst_element_dispose(). But I think
gst_scheduler_element_remove(element, element->sched) needs to be
called before, to allow for the scheduler to clean up its lists
"clock_providers" and "clock_receivers" and its data field "parent".

Is there a document describing somewhere what object holds references
to what other objects (and when)?
If not we should really get such a document somewhere.

The scheduler should be properly updated when the element is removed
from the bin.