#1 support for du --exclude switch

[Diab Jerius]

Here's a first cut at support for the du --exclude
switch. We have NetApps here which create snapshots,
and it's impossible to get reliable diskusage info
without excluding all of the .snapshot directories.

this patch also fixes what I believe is a typo
(proceeding => processing).

The patch is against version 1.2f

[Diab Jerius]