Update to version 3.4.0, which includes updated documentation, links to
the NEW GOES EAST Satellite imagery, and, among other things, a new pop3
client for fetching WX-ATLAN email and handing each NHC product from
these emails to JStrack's filter, filt.tcl.

The NHC's server, along with the rest of the world, went to HTTPS, and
that broke the HTTP filter. So, the HTTP filter is no longer supported.

Dependency on `graphics/netpbm' was removed because upstream had switched
to Tcl-based `Img' extension which apparently had not been ported yet.