dm thin: update stale "Status" Documentation

Documentation/device-mapper-/thin-provisioning.txt's "Status" section no
longer reflected the current fitness level of DM thin-provisioning.
That is, DM thinp is no longer "EXPERIMENTAL".  It has since seen
considerable improvement, has been fairly widely deployed and has
performed in a robust manner.

Update Documentation to dispel concern raised by potential DM thinp
users.
Reported-by: Drew Hastings <dhastings@crucialwebhost.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

Documentation/device-mapper/thin-provisioning.txt

@@ -28,17 +28,18 @@ administrator some freedom, for example to:
 Status
 ======
 
-These targets are very much still in the EXPERIMENTAL state.  Please
-do not yet rely on them in production.  But do experiment and offer us
-feedback.  Different use cases will have different performance
-characteristics, for example due to fragmentation of the data volume.
+These targets are considered safe for production use.  But different use
+cases will have different performance characteristics, for example due
+to fragmentation of the data volume.
 
 If you find this software is not performing as expected please mail
 dm-devel@redhat.com with details and we'll try our best to improve
 things for you.
 
-Userspace tools for checking and repairing the metadata are under
-development.
+Userspace tools for checking and repairing the metadata have been fully
+developed and are available as 'thin_check' and 'thin_repair'.  The name
+of the package that provides these utilities varies by distribution (on
+a Red Hat distribution it is named 'device-mapper-persistent-data').
 
 Cookbook
 ========