Add version-specific defines for each C interface.

ppapi/c/dev/ppb_file_system_dev.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_DEV_PPB_FILE_SYSTEM_DEV_H_
 #define PPAPI_C_DEV_PPB_FILE_SYSTEM_DEV_H_
 
 #include "ppapi/c/dev/pp_file_info_dev.h"
 #include "ppapi/c/pp_bool.h"
 #include "ppapi/c/pp_instance.h"
 #include "ppapi/c/pp_resource.h"
 #include "ppapi/c/pp_stdint.h"
 #include "ppapi/c/pp_time.h"
 
 struct PP_CompletionCallback;
 
-#define PPB_FILESYSTEM_DEV_INTERFACE "PPB_FileSystem(Dev);0.5"
+#define PPB_FILESYSTEM_DEV_INTERFACE_0_5 "PPB_FileSystem(Dev);0.5"
+#define PPB_FILESYSTEM_DEV_INTERFACE PPB_FILESYSTEM_DEV_INTERFACE_0_5
 
 struct PPB_FileSystem_Dev {
   /** Creates a filesystem object of the given type. */
   PP_Resource (*Create)(PP_Instance instance, PP_FileSystemType_Dev type);
 
   /** Returns PP_TRUE if the given resource is a FileSystem. */
   PP_Bool (*IsFileSystem)(PP_Resource resource);
 
   /**
    * Opens the file system. A file system must be opened before running any
@@ skipping 10 matching lines @@
    * Returns the type of the given file system.
    *
    * Returns PP_FILESYSTEMTYPE_INVALID if the given resource is not a valid
    * filesystem. It is valid to call this function even before Open completes.
    */
   PP_FileSystemType_Dev (*GetType)(PP_Resource file_system);
 };
 
 #endif  /* PPAPI_C_DEV_PPB_FILE_SYSTEM_DEV_H_ */