screenShield: Forward key presses to tne entry when raising the shield

https://bugzilla.gnome.org/show_bug.cgi?id=686740

js/ui/unlockDialog.js

@@ -300,4 +300,8 @@ const UnlockDialog = new Lang.Class({
 
         this.destroy();
     },
+
+    addCharacter: function(unichar) {
+        this._promptEntry.clutter_text.insert_unichar(unichar);
+    },
 });