code for local subnet definitions

[chuhn]

This is required if the DHCP server is only queried by relays and does not serve its local subnet(s).
Without such a definition it refuses to start:

dhcpd: No subnet declaration for eth0 (…).
dhcpd: ** Ignoring requests on eth0. If this is not what
dhcpd: you want, please write a subnet declaration
dhcpd: in your dhcpd.conf file for the network segment
dhcpd: to which interface eth0 is attached. **
dhcpd:
dhcpd:
dhcpd: Not configured to listen on any interfaces!

The proposed canonical solution is to add an empty definition: subnet … netmask … {}.

But this patch calls subnet_conf which inserts the complete subnet definition with DHCP options etc. That works for me. Anyhow I can extend the patch to generate empty definitions if you prefer.

[chuhn]

Ping?