Cleanup semaphore<> (sema.h) and mutex.h (shared_mutex)

Remove semaphore_lock and writer_lock classes, replace with std::lock_guard
Change semaphore<> interface to Lockable (+ exotic try_unlock method)

Utilities/sync.h

@@ -65,7 +65,7 @@ inline int futex(int* uaddr, int futex_op, int val, const timespec* timeout, int
 
 		int operator()(int* uaddr, int futex_op, int val, const timespec* timeout, int*, uint val3)
 		{
-			std::unique_lock<std::mutex> lock(mutex);
+			std::unique_lock lock(mutex);
 
 			switch (futex_op)
 			{