Fill in implementation of CommWait before large changes
This commit adds the implementation of the extension
set computation before larger changes are added into
the UDPOR implementation.
What was discovered is that events hold stale references
to the transitions that they own. As UDPOR executes
actors in its quest to search the unfolding of the
application, the transitions that are executed are
potentially updated with additional information
*after* they have been executed. We'll need a way
to figure out how to manage this without causing an
absolute mess...
