for rc6, add descriptions for currentOp/serverStatus output for lockStats;

acquireCount - Number of times the lock was acquired in the specified mode (regardless of whether the lock acquisition had to wait or not).
acquireWaitCount - Number of times the above lock acqusitions had to wait, because the lock was held in a conflicting mode. This value is always less than the acquireCount.
timeAcquiringMicros - Cummulative time lock aquisitions waited, because the lock was held in a conflicting mode (in microseconds). timeAcquiringMicros/acquireWaitCount gives an approximate average wait time for the particular lock mode.
deadlockCount - Number of times lock acquisitions encountered deadlock when they waited for a lock to be granted. This value should be very low.