lay base for the actual dialog

also make EmuSettingsDialog properly modal

src/frontend/qt_sdl/EmuSettingsDialog.h

@@ -42,7 +42,7 @@ public:
         }
 
         currentDlg = new EmuSettingsDialog(parent);
-        currentDlg->show();
+        currentDlg->open();
         return currentDlg;
     }
     static void closeDlg()