- Implement KiAcquireDispatcherObject, KiReleaseDispatcherObject, used on SMP for...

- Implement KiAcquireDispatcherObject, KiReleaseDispatcherObject, used on SMP for dispatcher objects which use the volatile long member in the dispatcher header (such as gates).
- Implement KiTryThreadLock which tries to acquire the lock but exits if it can't, isntead of looping.
- Re-factor KeWaitForGate to make it SMP-safe by acquiring various locks when required.
- Fixed up KeSignalGateBoostPriority so it can also be SMP-safe, and also fix what exactly happens when the gate is signaled (directly make the other thread ready instead of doing a KiUnwaitThread on it).
- Split KxAcquireSpinLock/KxReleaseSpinLock into SMP vs UP like the other routines.

svn path=/trunk/; revision=24103