Fix timing drift on CoreTiming::ForceCheck().

Since -1 -(-1) = 0, we'll never think we moved forward this way.

Core/CoreTiming.cpp

@@ -572,7 +572,7 @@ void ForceCheck()
 	// This will cause us to check for new events immediately.
 	currentMIPS->downcount = -1;
 	// But let's not eat a bunch more time in Advance() because of this.
-	slicelength = 1;
+	slicelength = -1;
 }
 
 void Advance()

Core/MIPS/IR/IRJit.cpp

@@ -149,7 +149,7 @@ bool IRJit::ReplaceJalTo(u32 dest) {
 }
 
 void IRBlockCache::Clear() {
-	for (size_t i = 0; i < blocks_.size(); ++i) {
+	for (int i = 0; i < size_; ++i) {
 		blocks_[i].Destroy(i);
 	}
 	blocks_.clear();