5179 remove unused ZFS ARC functions

*** 81,92 ****
          ARC_SPACE_NUMTYPES
  } arc_space_type_t;
  
  void arc_space_consume(uint64_t space, arc_space_type_t type);
  void arc_space_return(uint64_t space, arc_space_type_t type);
- void *arc_data_buf_alloc(uint64_t space);
- void arc_data_buf_free(void *buf, uint64_t space);
  arc_buf_t *arc_buf_alloc(spa_t *spa, int size, void *tag,
      arc_buf_contents_t type);
  arc_buf_t *arc_loan_buf(spa_t *spa, int size);
  void arc_return_buf(arc_buf_t *buf, void *tag);
  void arc_loan_inuse_buf(arc_buf_t *buf, void *tag);
--- 81,90 ----