Add subcalc, a utility that is used for subnet calculation and IPv6
DNS PTR record generation. subcalc takes command line arguments in
a similar format to ifconfig(8) so the synopsis should be familiar to
the user. Given an address family, address and a netmask/prefix
length, subcalc will calculate the number of hosts and address ranges
of the specific network.
Submitted by: Chris S.J. Peron