menu-bar: disable items when no frame visible

[David Reitter]

This patch ensures that menu items are disabled when they should be,  
i.e. when there is no applicable visible and non-iconified frame.
In a lot of cases, one could do "insert file" or choose stuff from  
the "search" menu even if there were only iconified or hidden frames.

menu-bar-visible-frame.patch
Description: Binary data

smime.p7s
Description: S/MIME cryptographic signature