amreport broken between 2.4.1p1 and 2.4.2

[Grant Beattie]

The email output of amreport seems to have been broken somewhere between
2.4.1p1 and 2.4.2.

The column widths are incorrectly determined and the output is particularly
messy with large file systems (and/or large lengths of time, etc).

It would also make more sense (to me, at least) for the output figures to be
represented in Mb and Mb/sec rather than Kb and Kb/sec. This would probably
help the email readability.

Comments, thoughts?

g.