Tests: Invalid project files.
Support Vala 0.21.1 (libvala-0.22).

 * Fix recognition of odd minor version numbers.
GTK_STOCK transition (partially).

 * Since Gtk 3.10 GTK_STOCK is deprecated so replace it. See also migration
   document[1].
   Some stock values are currently hardcoded (only transitional):
    - libgdl has not deprecated stock items yet so keep using
      Gdl.DockItem.with_stock. There is Gdl.DockItem.with_pixbuf_icon but
      perhaps there will come an icon_name property.
    - libgtksourceview has changed with 3.9.3 which is currently not
      installed on my system, so wait for proper transition.

    Some icons are gone from dialogs. If they are important they have to
    be added manually.

 NOTE: Do not forget to track theme changes and change icons loaded by
       Gtk.IconTheme.load_icon.

[1]: https://docs.google.com/document/d/1KCVPoYQBqMbDP11tHPpjW6uaEHrvLUmcDPqKAppCY8o/pub
Include mnemonic strings fully into gettext string.

 * Important because difference of word starting is locale dependant.
Use proper solution for #695972 since gdl >= 3.8.

 * stock-id update works well since gdl 3.8.1 (add new define GDL_3_8).