Add version-specific defines for each C interface.

ppapi/c/dev/ppb_zoom_dev.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_DEV_PPB_ZOOM_DEV_H_
 #define PPAPI_C_DEV_PPB_ZOOM_DEV_H_
 
 #include "ppapi/c/pp_instance.h"
 
 // Zoom interface should only apply to those full-page "plugin-document".
-#define PPB_ZOOM_DEV_INTERFACE "PPB_Zoom(Dev);0.2"
+#define PPB_ZOOM_DEV_INTERFACE_0_2 "PPB_Zoom(Dev);0.2"
+#define PPB_ZOOM_DEV_INTERFACE PPB_ZOOM_DEV_INTERFACE_0_2
 
 struct PPB_Zoom_Dev {
   // Informs the browser about the new zoom factor for the plugin (see
   // ppp_zoom_dev.h for a description of zoom factor). The plugin should only
   // call this function if the zoom change was triggered by the browser, it's
   // only needed in case a plugin can update its own zoom, say because of its
   // own UI.
   void (*ZoomChanged)(PP_Instance instance,
                       double factor);
 
   // Sets the mininum and maximium zoom factors.
   void (*ZoomLimitsChanged)(PP_Instance instance,
                             double minimum_factor,
                             double maximium_factor);
 };
 
 #endif  /* PPAPI_C_DEV_PPB_ZOOM_DEV_H_ */