dm table: add immutable feature

Introduce DM_TARGET_IMMUTABLE to indicate that the target type cannot be mixed
with any other target type, and once loaded into a device, it cannot be
replaced with a table containing a different type.

The thin provisioning pool device will use this.

Signed-off-by: Alasdair G Kergon <agk@redhat.com>
diff --git a/include/linux/dm-ioctl.h b/include/linux/dm-ioctl.h
index 0cb8eff..75fd5573 100644
--- a/include/linux/dm-ioctl.h
+++ b/include/linux/dm-ioctl.h
@@ -267,9 +267,9 @@
 #define DM_DEV_SET_GEOMETRY	_IOWR(DM_IOCTL, DM_DEV_SET_GEOMETRY_CMD, struct dm_ioctl)
 
 #define DM_VERSION_MAJOR	4
-#define DM_VERSION_MINOR	21
+#define DM_VERSION_MINOR	22
 #define DM_VERSION_PATCHLEVEL	0
-#define DM_VERSION_EXTRA	"-ioctl (2011-07-06)"
+#define DM_VERSION_EXTRA	"-ioctl (2011-10-19)"
 
 /* Status bits */
 #define DM_READONLY_FLAG	(1 << 0) /* In/Out */