I'm gonna want to have nested event loops sooner or later, so let's not
pollute GEventLoop with things that are meant to work globally.
This patch also changes key events to pass around their modifiers as a
bitfield all the way around the system instead of breaking them up.
This patch adds a GShortcut class. Each GAction can have a GShortcut which
will cause the event loop to listen for that key combination app-globally
and activate the event in case it's pressed.
The shortcut will also be displayed when the action is added to a menu.
Use this to hook up Alt+Up with the "open parent directory" action in the
FileManager app. :^)
