Use LOCK macros for non-recursive locks

Instead of std::unique_lock.

src/sync.h

@@ -112,9 +112,6 @@ typedef AnnotatedMixin<std::mutex> CWaitableCriticalSection;
 /** Just a typedef for std::condition_variable, can be wrapped later if desired */
 typedef std::condition_variable CConditionVariable;
 
-/** Just a typedef for std::unique_lock, can be wrapped later if desired */
-typedef std::unique_lock<std::mutex> WaitableLock;
-
 #ifdef DEBUG_LOCKCONTENTION
 void PrintLockContention(const char* pszName, const char* pszFile, int nLine);
 #endif