tests/icles/metadata_editor.*: Remove GstXOverlay stuff and use gdkpixbufsink plus some rather crude drawing/scaling ...

Original commit message from CVS:
* tests/icles/metadata_editor.c: (ENC_UNKNOWN), (last_pixbuf),
(draw_pixbuf), (change_tag_list), (update_draw_pixbuf),
(ui_drawing_size_allocate_cb), (on_drawingMain_expose_event),
(on_buttonSaveFile_clicked), (ui_create), (me_gst_bus_callback_view),
(me_gst_setup_view_pipeline), (process_file):
* tests/icles/metadata_editor.glade:
Remove GstXOverlay stuff and use gdkpixbufsink plus some rather crude
drawing/scaling logic to make this compile and work on all platforms.
Fixes #518227.