lock.c: Separate DETECT_DEADLOCKS from DEBUG_THREADS

lock.c: Separate DETECT_DEADLOCKS from DEBUG_THREADS

Previously, DETECT_DEADLOCKS depended on DEBUG_THREADS.
Unfortunately, DEBUG_THREADS adds a lot of lock tracking overhead
to all of the lock lifecycle calls whereas DETECT_DEADLOCKS just
causes the lock calls to loop over trylock in 200us intervals until
the lock is obtained and spits out log messages if it takes more
than 5 seconds.  From a code perspective, the only reason they were
tied together was for logging.  So... The ifdefs in lock.c were
refactored to allow DETECT_DEADLOCKS to be enabled without
also enabling DEBUG_THREADS.

Resolves: #321

UserNote: You no longer need to select DEBUG_THREADS to use
DETECT_DEADLOCKS.  This removes a significant amount of overhead
if you just want to detect possible deadlocks vs needing full
lock tracing.