Possibility to physically reserve space without writing leaf blocks

*** 134,143 ****
--- 134,144 ----
  
  /*
   * boot archive compression
   */
  #define _FIO_COMPRESSED         _IO('f', 99) /* mark file as compressed */
+ #define _FIO_RESERVE_SPACE      _IO('f', 100) /* Reserve space */
  
  #ifdef  __cplusplus
  }
  #endif