Add support for disabling ", Private network ..." from output

[troglobit]

Jerry Przybylski writes:

A feature to suppress the output of "Reserved" IPs per RFC 1918 part 3 would be another nice feature.

I'm assuming you mean a way to disable the text after the comma in the output:

Hosts/Net: 254                   Class C, Private network (RFC1918)
                                        ~~~~~~~~~~~~~~~~~~~~~~~~~~~

Sure this could a be a pre-runtime flag to the configure script, or a command line option to netcalc itself. Also a very good task for a newcomer to the project :)