gtk-demo: Rename image scaling demo to image_scaling

This just means renaming the C file, but it makes --run=image_scaling
actually do what I'd expect.

demos/gtk-demo/demo.gresource.xml

@@ -298,6 +298,7 @@
     <file>iconscroll.c</file>
     <file>iconview.c</file>
     <file>iconview_edit.c</file>
+    <file>image_scaling.c</file>
     <file>images.c</file>
     <file>infobar.c</file>
     <file>layoutmanager.c</file>
@@ -318,7 +319,6 @@
     <file>main.c</file>
     <file>markup.c</file>
     <file>mask.c</file>
-    <file>menu.c</file>
     <file>overlay.c</file>
     <file>overlay_decorative.c</file>
     <file>paint.c</file>

demos/gtk-demo/image_scaling.c

@@ -117,7 +117,7 @@ transform_from (GBinding     *binding,
 }
 
 GtkWidget *
-do_menu (GtkWidget *do_widget)
+do_image_scaling (GtkWidget *do_widget)
 {
   static GtkWidget *window = NULL;
 

demos/gtk-demo/meson.build

@@ -39,6 +39,7 @@ demos = files([
   'iconscroll.c',
   'iconview.c',
   'iconview_edit.c',
+  'image_scaling.c',
   'images.c',
   'infobar.c',
   'layoutmanager.c',
@@ -47,7 +48,6 @@ demos = files([
   'listbox.c',
   'listbox_controls.c',
   'mask.c',
-  'menu.c',
   'flowbox.c',
   'list_store.c',
   'listview_applauncher.c',