X11Utils: Don't depend on wx

We want to have two build targets: Main and MainNoGUI, and this code
will be linked against in both cases, so the ifdef isn't enough for
this case.

Just append to a vector of strings, and then convert it after the fact.

Source/Core/DolphinWX/X11Utils.h

@@ -51,9 +51,7 @@ class XRRConfiguration
 
 		void Update();
 		void ToggleDisplayMode(bool bFullscreen);
-#if defined(HAVE_WX) && HAVE_WX
-		void AddResolutions(wxArrayString& arrayStringFor_FullscreenResolution);
-#endif
+		void AddResolutions(std::vector<std::string>& resos);
 
 	private:
 		Display *dpy;