GUAC-998: Add left/right meta to list of possible "Alt" keys. Some systems interpret Shift+Alt as Shift+Meta.

guacamole/src/main/webapp/app/client/controllers/clientController.js

@@ -62,9 +62,10 @@ angular.module('client').controller('clientController', ['$scope', '$routeParams
      * In order to open the guacamole menu, we need to hit ctrl-alt-shift. There are
      * several possible keysysms for each key.
      */
-    var SHIFT_KEYS  = {0xFFE1 : true, 0xFFE2: true},
-        ALT_KEYS    = {0xFFE9 : true, 0xFFEA : true, 0xFE03: true},
-        CTRL_KEYS   = {0xFFE3 : true, 0xFFE4: true},
+    var SHIFT_KEYS  = {0xFFE1 : true, 0xFFE2 : true},
+        ALT_KEYS    = {0xFFE9 : true, 0xFFEA : true, 0xFE03 : true,
+                       0xFFE7 : true, 0xFFE8 : true},
+        CTRL_KEYS   = {0xFFE3 : true, 0xFFE4 : true},
         MENU_KEYS   = angular.extend({}, SHIFT_KEYS, ALT_KEYS, CTRL_KEYS);
 
     /**