Core: Don't pass through a reference to the window handle

Now that MainNoGUI is properly architected and GLX doesn't need to
sometimes craft its own windows sometimes which we have to thread back
into MainNoGUI, we don't need to thread the window handle that GLX
creates at all.

This removes the reference to pass back here, and the g_pWindowHandle
always be the same as the window returned by Host_GetRenderHandle().

A future cleanup could remove g_pWindowHandle entirely.

Source/Core/DolphinWX/MainNoGUI.cpp

@@ -31,6 +31,7 @@ class Platform
 {
 public:
 	virtual void Init() = 0;
+	virtual void SetTitle(const std::string &title) = 0;
 	virtual void MainLoop() = 0;
 	virtual void Shutdown() = 0;
 	virtual ~Platform() {};
@@ -58,7 +59,10 @@ void* Host_GetRenderHandle()
 	return windowHandle;
 }
 
-void Host_UpdateTitle(const std::string& title){};
+void Host_UpdateTitle(const std::string& title)
+{
+	platform->SetTitle(title);
+}
 
 void Host_UpdateDisasmDialog(){}
 
@@ -175,6 +179,11 @@ class PlatformX11 : public Platform
 		}
 	}
 
+	void SetTitle(const std::string &string) override
+	{
+		XStoreName(dpy, win, string.c_str());
+	}
+
 	void MainLoop() override
 	{
 		bool fullscreen = SConfig::GetInstance().m_LocalCoreStartupParameter.bFullscreen;