include/input.js: change to LGPL-2 or later.

Requested by Alexander Larsson at Red Hat to allow incorporation of
solution into HTML5 gtk 3.0 backend.

LICENSE.txt

 noVNC is licensed under the LGPL version 3 (see docs/LICENSE.GPL-3 and
 docs/LICENSE.LGPL-3) with the following exceptions:
 
+    include/input.js           : LGPL-2 or any later version
+   
     include/base64.js          : Dual GPL-2 or LGPL-2.1
    
     incluee/des.js             : Various BSD style licenses

include/input.js

 /*
  * noVNC: HTML5 VNC client
  * Copyright (C) 2011 Joel Martin
- * Licensed under LGPL-3 (see LICENSE.txt)
+ * Licensed under LGPL-2 or any later version (see LICENSE.txt)
  */
 
 /*jslint browser: true, white: false, bitwise: false */