rpki-client: disallow empty sets of IP Addresses or AS numbers

rpki-client: disallow empty sets of IP Addresses or AS numbers

RFC 3779 doesn't say anything about empty lists of IP addresses and AS
numbers. Of course the RFC 3779 code in libcrypto implements a check for
empty lists for AS numbers but fails to do so for IP addresses...

While RFC 6487 is explicit about disallowing empty lists of IP addresses,
it is not explicit about disallowing empty ipAddressesOrRanges, but that
seems to be the intent.

Found with BBN test corpora

ok job