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

*** 427,436 ****
--- 427,438 ----
          zprop_register_hidden(ZFS_PROP_STMF_SHAREINFO, "stmf_sbd_lu",
              PROP_TYPE_STRING, PROP_INHERIT, ZFS_TYPE_VOLUME,
              "STMF_SBD_LU");
          zprop_register_hidden(ZFS_PROP_GUID, "guid", PROP_TYPE_NUMBER,
              PROP_READONLY, ZFS_TYPE_DATASET | ZFS_TYPE_BOOKMARK, "GUID");
+         zprop_register_hidden(ZFS_PROP_FSID_GUID, "fsid_guid", PROP_TYPE_NUMBER,
+             PROP_DEFAULT, ZFS_TYPE_DATASET, "FSIDGUID");
          zprop_register_hidden(ZFS_PROP_USERACCOUNTING, "useraccounting",
              PROP_TYPE_NUMBER, PROP_READONLY, ZFS_TYPE_DATASET,
              "USERACCOUNTING");
          zprop_register_hidden(ZFS_PROP_UNIQUE, "unique", PROP_TYPE_NUMBER,
              PROP_READONLY, ZFS_TYPE_DATASET, "UNIQUE");