Rework the warnings on internet resources

Rework the warnings on internet resources

Unify the printing of warnings about AS numbers and IP address blocks to
use a call to as_warn() and ip_warn(). Fix a bug in the latter where the
upper bound of an IP range didn't take the RFC 3779 encoding into account
and passed the address directly to inet_pton() rather than filling the
missing bits with 1. Switch the argument order to match the warnings and
tweak some warning messages.

ok claudio job