Possibility to physically reserve space without writing leaf blocks

*** 373,382 ****
--- 373,385 ----
  #define BP_SET_TYPE(bp, x)              BF64_SET((bp)->blk_prop, 48, 8, x)
  
  #define BP_GET_LEVEL(bp)                BF64_GET((bp)->blk_prop, 56, 5)
  #define BP_SET_LEVEL(bp, x)             BF64_SET((bp)->blk_prop, 56, 5, x)
  
+ #define BP_GET_PROP_RESERVATION(bp)          BF64_GET((bp)->blk_prop, 61, 1)
+ #define BP_SET_PROP_RESERVATION(bp, x)       BF64_SET((bp)->blk_prop, 61, 1, x)
+ 
  #define BP_GET_DEDUP(bp)                BF64_GET((bp)->blk_prop, 62, 1)
  #define BP_SET_DEDUP(bp, x)             BF64_SET((bp)->blk_prop, 62, 1, x)
  
  #define BP_GET_BYTEORDER(bp)            BF64_GET((bp)->blk_prop, 63, 1)
  #define BP_SET_BYTEORDER(bp, x)         BF64_SET((bp)->blk_prop, 63, 1, x)