Use clutter_event_get_* instead of ShellGlobal

Before Clutter gained accessors for event information, we had
shell_global_ functions.  Now that Clutter has them, use them and
delete the ShellGlobal code.

http://bugzilla.gnome.org/show_bug.cgi?id=594561

js/ui/lookingGlass.js

@@ -418,7 +418,7 @@ LookingGlass.prototype = {
             return true;
         }));
         this._entry.connect('key-press-event', Lang.bind(this, function(o, e) {
-            let symbol = Shell.get_event_key_symbol(e);
+            let symbol = e.get_key_symbol();
             if (symbol == Clutter.Escape) {
                 this.close();
                 return true;