cstyle fixes
dsl_dataset_set_fsid_guid should use ZFS_SPACE_CHECK_RESERVED
dsl_dataset_set_fsid_guid _check and _sync func declared static,
removed from dsl_dataset.h
rewrite unique_valid
6333 ZFS should let the user specify or modify the fsid_guid of a dataset

*** 2402,2411 ****
--- 2402,2414 ----
                  return (-1);
  
          VERIFY(0 == nvpair_value_uint64(pair, &intval));
  
          switch (prop) {
+         case ZFS_PROP_FSID_GUID:
+                 err = dsl_dataset_set_fsid_guid(dsname, source, intval);
+                 break;
          case ZFS_PROP_QUOTA:
                  err = dsl_dir_set_quota(dsname, source, intval);
                  break;
          case ZFS_PROP_REFQUOTA:
                  err = dsl_dataset_set_refquota(dsname, source, intval);