6070 libdisasm: attach/detach arch ops should be optional
Reviewed by: Robert Mustacchi <rm@joyent.com>

*** 141,151 ****
--- 141,153 ----
  }
  
  void
  dis_handle_destroy(dis_handle_t *dhp)
  {
+         if (dhp->dh_arch->da_handle_detach != NULL)
                  dhp->dh_arch->da_handle_detach(dhp);
+ 
          dis_free(dhp, sizeof (dis_handle_t));
  }
  
  dis_handle_t *
  dis_handle_create(int flags, void *data, dis_lookup_f lookup_func,
*** 179,189 ****
  
          /*
           * Allow the architecture-specific code to allocate
           * its private data.
           */
!         if (arch->da_handle_attach(dhp) != 0) {
                  dis_free(dhp, sizeof (dis_handle_t));
                  /* dis errno already set */
                  return (NULL);
          }
  
--- 181,192 ----
  
          /*
           * Allow the architecture-specific code to allocate
           * its private data.
           */
!         if (arch->da_handle_attach != NULL &&
!             arch->da_handle_attach(dhp) != 0) {
                  dis_free(dhp, sizeof (dis_handle_t));
                  /* dis errno already set */
                  return (NULL);
          }