[Reviewer Andy] Timer C support

Andy

Can you review the changes to add support for Timer C.  I've tested in UTs, not live.

Note that I haven't fixed in stateful_proxy, so Bono won't have support for Timer C.  I think this is okay for now (until we move Bono/P-CSCF function into Sproutlet-land).

Mike

Can we log what the event was too?