rank order violation when alarm arrives in deadlock code

<rank order violation shared_itimer_lock(recursive)@third_party/dynamorio/trunk/core/unix/signal.c:1496 acquired after innermost_lock(mutex)@third_party/dynamorio/trunk/core/utils.c:223 in tid:1d767>
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innermost_lock is grabbed inside various process lock handling routines (debug-only) so an alarm that arrives there could hit this. Maybe we should check and drop the signal if this happens?

We do not expect any problems in release build.