4370 avoid transmitting holes during zfs send
4371 DMU code clean up
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Christopher Siden <christopher.siden@delphix.com>
Reviewed by: Josef 'Jeff' Sipek <jeffpc@josefsipek.net>
Approved by: Garrett D'Amore <garrett@damore.org>
Issue #9: Support for persistent CoS/vdev attributes with feature flags
          Support for feature flags for special tier
          Contributors: Daniil Lunev, Boris Protopopov

*** 40,49 ****
--- 40,54 ----
  
  struct spa;
  struct dmu_tx;
  struct objset;
  
+ #define FEATURE_META_DEVICES "feature@meta_devices"
+ 
+ extern boolean_t feature_is_supported(struct objset *os, uint64_t obj,
+     uint64_t desc_obj, nvlist_t *unsup_feat, nvlist_t *enabled_feat);
+ 
  extern void spa_feature_create_zap_objects(struct spa *, struct dmu_tx *);
  extern void spa_feature_enable(struct spa *, spa_feature_t,
      struct dmu_tx *);
  extern void spa_feature_incr(struct spa *, spa_feature_t, struct dmu_tx *);
  extern void spa_feature_decr(struct spa *, spa_feature_t, struct dmu_tx *);