docs/162438: du(1) man page improvements

[Alexander Best]

On Fri Nov 11 11, Benjamin Kaduk wrote:
> On Fri, 11 Nov 2011, Alexander Best wrote:
> 
> >here's another revised version of my patch. this now also includes changes
> >to du.c:usage() to reflect the man page changes.
> 
> Looks okay to me -- thanks.

good to hear. now we need somebody to commit this. ;)

> 
> -Ben