It seems most GTK apps like mintMenu and the default Gnome2/Mate menu
use the GDK grab focus functions to grab input (pointer/keyboard).
These functions appear to suck all input to the app like a blackhole.
This patch gives more interactivity to the mintMenu window, making it
a first class object in the desktop.
Things that work now:
* When the window is open, hovering on other desktop icons highlights them
* Clicking outside the window propagates the event (e.g. select another
window)
* Alt-tab and other events unfocus and hide the window
* Scrollbars in the mintMenu finally work right
* Probably several other small things
