release methods must release resources even were the underlying OpenMP entity has disappeared

[ariel-rw]

In working with OMPD a couple of practical issues have come up.
One of these relates to releasing handles. Specifically,
it can happen that by the time the debugger is able to release
a handle, say for a thread, the thread itself has disappeared.
In these cases we need the debugger to be able to release the
handle so that the OMPD can release any resources it may be
holding. The OMPD needs to be able to do its clean up even
if the thing to which the handle refers has disappeared.

This should apply to all handles: parallel region handles, task handle,
etc., etc..

Oncve we've agreed this, ee are going to need some language
in the document.