updating the scm (and slib) port

[Wim Lewis <wiml_(_at_)_hhhh_(_dot_)_org>]

I need a newer version of scm than is in the ports tree, so I thought I'd
try my hand at updating the port. I don't see any recent mention of scm on
this list, so can I assume that no one else is currently attacking this
and I'm not just wasting my time on duplicated effort?

I notice that the netbsd port is only one version out of date, so I'll
probably use that as a stepping-stone.

I haven't messed with ports from the maintainer side before: are there any
pitfalls or recent changes in direction that I should be aware of?

Any advice is welcome,
   Wim