zfs-create(8): grammar, caution

Make the heading more generic. The subtexts are not solely about ZFS volumes.

Grammar: remove the second of the three 'the' words from the phrase below.

… After creating the volume with the zfs create -V enable the …

Insert a comma.

Singular, not plural.

Whilst here, express caution. Consider <#7734> (Swap deadlock in 0.7.9).

man/man8/zfs-create.8

@@ -234,14 +234,16 @@ if the volume is not sparse.
 Print verbose information about the created dataset.
 .El
 .El
-.Ss ZFS Volumes as Swap
-ZFS volumes may be used as swap devices.
-After creating the volume with the
-.Nm zfs Cm create Fl V
+.Ss ZFS for Swap
+Swapping to a ZFS volume is possible, however care must be taken to avoid
+deadlocks.
+After creating the volume with
+.Nm zfs Cm create Fl V ,
 enable the swap area using the
 .Xr swapon 8
 command.
-Swapping to files on ZFS filesystems is not supported.
+.Pp
+Swapping to a file on a ZFS filesystem is not supported.
 .
 .Sh EXAMPLES
 .\" These are, respectively, examples 1, 10 from zfs.8