Header optimizations (#1684)

Shouldn't break anything. I hope.

Utilities/SharedMutex.h

@@ -35,11 +35,11 @@ class shared_mutex final
 public:
 	constexpr shared_mutex() = default;
 
-	~shared_mutex();
-
 	// Initialize internal data
 	void initialize_once();
 
+	~shared_mutex();
+
 	bool try_lock_shared()
 	{
 		auto ctrl = m_ctrl.load();