[Reviewer Matt] Add deadlock detection to eventq

Matt

Can you review the cpp-common changes adding deadlock detection to the eventq.  I'll send a subsequent pull request for the Sprout changes once this is pulled to the master branch.

There's also a minor change to the load monitor to fix a NaN sometimes displayed in logs.

Mike
Likewise, why do we reset this?  It's probably worth commenting on the method definition that you should only set the deadlock threshold during initialization.