gsdx: add atomic for transaction scope object

plugins/GSdx/GSThread.h

@@ -30,30 +30,31 @@ class TransactionScope
 public:
 	class Lock
 	{
-		volatile long state;
+		std::atomic<bool> state;
 
 	public:
 		Lock()
-			: state(0) 
+			: state(false)
 		{
 		}
 
 		void lock()
 		{
-			while(_InterlockedCompareExchange(&state, 1, 0) != 0)
+			bool expected_value = false;
+			while(state.compare_exchange_strong(expected_value, true))
 			{
-				do {_mm_pause();} while(state == 1);
+				do {_mm_pause();} while(state);
 			}
 		}
 
 		void unlock()
 		{
-			_InterlockedExchange(&state, 0);
+			state = false;
 		}
 
 		bool isLocked() const
 		{
-			return state == 1;
+			return state.load();
 		}
 	};