5045 use atomic_{inc,dec}_* instead of atomic_add_*

*** 3261,3271 ****
                  ap = np;
                  /* Inlined IPACT_REFRELE -- avoid recursion */
                  if (ap == NULL)
                          break;
                  membar_exit();
!                 if (atomic_add_32_nv(&(ap)->ipa_refs, -1) != 0)
                          break;
                  /* End inlined IPACT_REFRELE */
          }
  }
  
--- 3261,3271 ----
                  ap = np;
                  /* Inlined IPACT_REFRELE -- avoid recursion */
                  if (ap == NULL)
                          break;
                  membar_exit();
!                 if (atomic_dec_32_nv(&(ap)->ipa_refs) != 0)
                          break;
                  /* End inlined IPACT_REFRELE */
          }
  }