Removed an not working utility

src/misc/advanced_mutex.h

@@ -158,6 +158,9 @@ namespace std {
 			T t;
 	};
 
+	/*
+	 * ATTENTION: Not sure how/why, but this causes a double rwlock unlock sometimes (when used with std::unique_lock)
+	 * Do not use this!
 	class shared_recursive_mutex {
 			std::shared_mutex handle;
 		public:
@@ -274,6 +277,7 @@ namespace std {
 			std::atomic<std::size_t> count;
 			mutex_guarded<std::map<std::thread::id, std::size_t>> shared_counts;
 	};
+	 */
 
 	template <typename T>
 	inline bool mutex_locked(T& mutex) {