SCTP service name to number translation clashes with TCP

[infrastation]

$ grep amqp /etc/services 
amqps		5671/tcp			# AMQP protocol over TLS/SSL
amqp		5672/tcp
amqp		5672/sctp

$ filtertest EN10MB 'sctp port amqp'
filtertest: port 'amqp' is tcp

The error message is from this block of gen_scode():

		if (proto == Q_SCTP) {
			if (real_proto == IPPROTO_UDP)
				bpf_error(cstate, "port '%s' is udp", name);

			else if (real_proto == IPPROTO_TCP)
				bpf_error(cstate, "port '%s' is tcp", name);
			else
				/* override PROTO_UNDEF */
				real_proto = IPPROTO_SCTP;
		}

Both the function and pcap-filter(7) imply that name to number translation is supposed to work for SCTP the same as it does for TCP and UDP. However, pcap_nametoport() is not aware of SCTP, so the documentation is different from the implementation.