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

@@ -45,10 +45,16 @@
 uint64_t unique_create(void);
 
 /* Return a unique value, which equals the one passed in if possible. */
 uint64_t unique_insert(uint64_t value);
 
+/*
+ * Return B_TRUE if the passed value does not exist and is valid,
+ * B_FALSE otherwise
+ */
+boolean_t unique_valid(uint64_t value);
+
 /* Indicate that this value no longer needs to be uniquified against. */
 void unique_remove(uint64_t value);
 
 #ifdef  __cplusplus
 }