When workspaces are disabled by the session mode, all workspace
related actions don't make sense. Worse, the "Move to Workspace ..."
actions allow sending windows into a nirvana with no means to
get them back.
https://bugzilla.gnome.org/show_bug.cgi?id=730653
The fallback app-menu in GTK+'s client side decorations obviously
uses the GTK+ theme rather than the shell one; update the style
of our own fallback app-menu to resemble that style.
https://bugzilla.gnome.org/show_bug.cgi?id=730752
We now allow "appmenu" in the button layout to make synchronizing it
with GTK+'s client-side decorations easier, but as some people tweak
their settings to get in-window app menus even when using the shell,
actually pop up the app menu when the button is activated.
https://bugzilla.gnome.org/show_bug.cgi?id=730752
