Remove "dbuf phys" db->db_data pointer aliases.

Use function accessors that cast db->db_data to the appropriate
"phys" type, removing the need for clients of the dmu buf user
API is keep properly typed pointer aliases to db->db_data in order
to conveniently access their data.

cmd/mdb/common/modules/zfs/Makefile.zfs:
cmd/mdb/intel/amd64/libzpool/Makefile:
cmd/mdb/intel/amd64/zfs/Makefile:
cmd/mdb/intel/ia32/libzpool/Makefile:
cmd/mdb/intel/ia32/zfs/Makefile:
cmd/mdb/sparc/v7/libzpool/Makefile:
cmd/mdb/sparc/v9/libzpool/Makefile:
cmd/mdb/sparc/v9/zfs/Makefile:
cmd/zdb/Makefile.com:
	Silence E_STATIC_UNUSED lint warnings.

cmd/mdb/common/modules/zfs/zfs.c:
uts/common/fs/zfs/zap_leaf.c:
	In zap_leaf() and zap_leaf_byteswap, now that the pointer alias
	field l_phys has been removed, use the db_data field in an on
	stack dmu_buf_t to point to the leaf's phys data.

uts/common/fs/zfs/dbuf.c:
	Remove the db_user_data_ptr_ptr field from dbuf and all logic
	to maintain it.

uts/common/fs/zfs/dbuf.c:
uts/common/fs/zfs/dnode.c:
uts/common/fs/zfs/sys/dbuf.h:
uts/common/fs/zfs/sys/dmu.h:
uts/common/fs/zfs/dsl_dataset.c:
uts/common/fs/zfs/dsl_dir.c:
uts/common/fs/zfs/sa.c:
uts/common/fs/zfs/zap.c:
uts/common/fs/zfs/zap_micro.c:
	Modify the DMU buf user API to remove the ability to specify
	a db_data aliasing pointer (db_user_data_ptr_ptr).

cmd/zdb/zdb.c:
uts/common/fs/zfs/dmu_diff.c:
uts/common/fs/zfs/dmu_objset.c:
uts/common/fs/zfs/dmu_send.c:
uts/common/fs/zfs/dmu_traverse.c:
uts/common/fs/zfs/dmu_tx.c:
uts/common/fs/zfs/dsl_bookmark.c:
uts/common/fs/zfs/dsl_dataset.c:
uts/common/fs/zfs/dsl_deadlist.c:
uts/common/fs/zfs/dsl_deleg.c:
uts/common/fs/zfs/dsl_destroy.c:
uts/common/fs/zfs/dsl_dir.c:
uts/common/fs/zfs/dsl_pool.c:
uts/common/fs/zfs/dsl_prop.c:
uts/common/fs/zfs/dsl_scan.c:
uts/common/fs/zfs/dsl_synctask.c:
uts/common/fs/zfs/dsl_userhold.c:
uts/common/fs/zfs/sa.c:
uts/common/fs/zfs/spa.c:
uts/common/fs/zfs/spa_history.c:
uts/common/fs/zfs/zap.c:
uts/common/fs/zfs/zap_leaf.c:
uts/common/fs/zfs/zap_micro.c:
uts/common/fs/zfs/zfs_ioctl.c:
uts/common/fs/zfs/sys/dsl_dataset.h:
uts/common/fs/zfs/sys/dsl_dir.h:
uts/common/fs/zfs/sys/zap_impl.h:
uts/common/fs/zfs/sys/zap_leaf.h:
	Create and use the new "phys data" accessor functions
	dsl_dir_phys(), dsl_dataset_phys(), zap_m_phys(),
	zap_f_phys(), and zap_leaf_phys().

uts/common/fs/zfs/sys/dsl_dataset.h:
uts/common/fs/zfs/sys/dsl_dir.h:
uts/common/fs/zfs/sys/zap_impl.h:
uts/common/fs/zfs/sys/zap_leaf.h:
	Remove now unused "phys pointer" aliases to db->db_data
	from clients of the DMU buf user API.