Illumos #1693: persistent 'comment' field for a zpool

Reviewed by: George Wilson <gwilson@zfsmail.com>
Reviewed by: Eric Schrock <eric.schrock@delphix.com>
Approved by: Richard Lowe <richlowe@richlowe.net>

References:
  https://www.illumos.org/issues/1693

Ported by: Martin Matuska <martin@matuska.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #678

include/sys/zfs_context.h

@@ -60,6 +60,7 @@
 #include <sys/zfs_debug.h>
 #include <sys/fm/fs/zfs.h>
 #include <sys/sunddi.h>
+#include <sys/ctype.h>
 #include <linux/dcache_compat.h>
 
 #else /* _KERNEL */
@@ -92,6 +93,7 @@
 #include <atomic.h>
 #include <dirent.h>
 #include <time.h>
+#include <ctype.h>
 #include <sys/note.h>
 #include <sys/types.h>
 #include <sys/cred.h>