vmstat: Fix alignment for disk partition format

vmstat: Fix alignment for disk partition format

The disk partition format translation hint, the actual text and the
printf statements were all diagreeing with each other. This meant
the disk partition output from vmstat was a mess.

Now all the titles and values line up and everything is right-aligned
which looks better than some half-hearted attempt at center-aligned
for titles and right-aligned for values.

Thanks to @goeran for the heads-up in #69