Allow FQDN instead of IP addresses

[eagle]

Ocat should allow fqdn's everywhere v4/v6 addresses
are used, resolve them, and use the resulting addresses.
Applies to -l, -o, -t, config file, etc.

Ocat should work in native or mixed v4/v6 environments.
Applies to -l, -t and the controller address. Maybe -4 and -6
flags as in common practice for this. ie: how sshd/sshd_config
and perhaps named do it.