Add version-specific defines for each C interface.

ppapi/c/ppb_core.h

 /* Copyright (c) 2010 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_CORE_H_
 #define PPAPI_C_PPB_CORE_H_
 
 #include "ppapi/c/pp_bool.h"
 #include "ppapi/c/pp_resource.h"
 #include "ppapi/c/pp_stdint.h"
 #include "ppapi/c/pp_time.h"
 #include "ppapi/c/pp_var.h"
 
 struct PP_CompletionCallback;
 
-#define PPB_CORE_INTERFACE "PPB_Core;0.4"
+#define PPB_CORE_INTERFACE_0_4 "PPB_Core;0.4"
+#define PPB_CORE_INTERFACE PPB_CORE_INTERFACE_0_4
 
 /**
  * @file
  * This file defines the PPB_Core interface defined by the browser and
  * and containing pointers to functions related to memory management,
  * time, and threads.
  */
 
 /**
  * @addtogroup Interfaces
@@ skipping 105 matching lines @@
    */
   PP_Bool (*IsMainThread)();
 };
 /**
  * @}
  */
 
 
 #endif  /* PPAPI_C_DEV_PPB_CORE_DEV_H_ */