HLE: Small kernel cleanups

Initialize the wokeThreads locals that were passed by reference uninitialized in
the event flag, VPL and semaphore timeout handlers. Harmless today since the
callee only ever assigns to them, but every other use in the same files starts
at false.

Do the semaphore overflow check in 64-bit, so a large signal value can't wrap
past it into currentCount.

Core/HLE/sceKernelMemory.cpp

@@ -1435,7 +1435,7 @@ void __KernelVplTimeout(u64 userdata, int cyclesLate) {
 	// If in FIFO mode, that may have cleared another thread to wake up.
 	VPL *vpl = kernelObjects.Get<VPL>(uid, error);
 	if (vpl && (vpl->nv.attr & PSP_VPL_ATTR_MASK_ORDER) == PSP_VPL_ATTR_FIFO) {
-		bool wokeThreads;
+		bool wokeThreads = false;
 		std::vector<VplWaitingThread>::iterator iter = vpl->waitingThreads.begin();
 		// Unlock every waiting thread until the first that must still wait.
 		while (iter != vpl->waitingThreads.end() && __KernelUnlockVplForThread(vpl, *iter, error, 0, wokeThreads)) {