Patch added for closing all spatial windows via menu and shortcut key

[Jamie <jamiemcc blueyonder co uk>]

Whilst hacking on Nautilus, I also created the following patch for
Nautilus enhancement request:

http://bugzilla.gnome.org/show_bug.cgi?id=142632

I choose Ctrl+Q as the shortcut key for closing all spatial windows at
once - sure beats having to type killall nautilus to get rid of all
those pesky popup spatial windows!

jamie.