bug#48783: Advertise support for Startup Notification when built with GTK

[Peter Oliver]

The specification for the Startup Notification Protocol 
(https://specifications.freedesktop.org/startup-notification-spec/startup-notification-latest.txt)
 says that we should put “StartupNotify=true” in our .desktop files if we 
support it.  Although we don’t cater for it directly, GTK gives us it for free 
from version 2.2 onwards 
(https://developer.gnome.org/platform-overview/stable/dev-launching-startupnotify.html.en).
  Hence, we should advertise support provided that this is a GTK build.

I have attached a patch to do this.

The practical effect of this change is that window managers will arrange for a 
slow to start Emacs to not steal the keyboard focus of a user who is typing 
into another application when Emacs pops onto the screen.

I have requested copyright assignment paperwork but am currently waiting to 
hear back.

--
Peter Oliver

0001-Advertise-support-for-Startup-Notification-when-buil.patch
Description: Text document