Documentation fixes for zfs(8)
* White space issue in the userused@user property section
* zfs send supports using bookmarks as the origin snapshot
Reviewed by: Ned Bass <bass6@llnl.gov>
Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: George Melikov <mail@gmelikov.ru>
Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov>
Signed-off-by: DHE <git@dehacked.net>
Closes#5906
f974e41426