Add version-specific defines for each C interface.

ppapi/c/ppb_messaging.h

 /* Copyright (c) 2011 The Chromium Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 #ifndef PPAPI_C_PPB_MESSAGING_H_
 #define PPAPI_C_PPB_MESSAGING_H_
 
 #include "ppapi/c/pp_instance.h"
 #include "ppapi/c/pp_var.h"
 
-#define PPB_MESSAGING_INTERFACE "PPB_Messaging;0.1"
+#define PPB_MESSAGING_INTERFACE_0_1 "PPB_Messaging;0.1"
+#define PPB_MESSAGING_INTERFACE PPB_MESSAGING_INTERFACE_0_1
 
 /**
  * @file
  * This file defines the PPB_Messaging interface implemented by the browser.
  * The PPB_Messaging interface contains pointers to functions related to
  * sending messages to the JavaScript onmessage handler on the DOM element
  * associated with a specific module instance.
  *
  * @addtogroup Interfaces
  * @{
@@ skipping 51 matching lines @@
    * The browser will pop-up an alert saying "Hello world!".
    */
   void (*PostMessage)(PP_Instance instance, struct PP_Var message);
 };
 /**
  * @}
  */
 
 #endif  /* PPAPI_C_PPB_MESSAGING_H_ */