kumar-v386.5-2: ddns: implement support for DYNV6.com

For dynv6.com to work correctly for setting DNS A record we need to
utilize the DynDNS API that is supported.  inadyn can handle this
via the 'custom' config (instead of dynv6 provider config).  The
config for inadyn looks like:

custom dynv6 {
	ddns-server = dynv6.com
	ddns-path = "/nic/update?hostname=%h&myip=%i"
	...
}

Update rc/services.c to handle this custom config, which is similar
to what is needed for WWW.NAMECHEAP.COM.

Signed-off-by: Kumar Gala <[email protected]>

kumar-v386.5: rc: start_wpa_supplicant: WIP for ATT 802.1x auth

Hack creation of /etc/wpa_supplicant-wan0.conf for what we need
it to look like to work for ATT internet.

Switch to using wpa_supplicant-2.7/wpa_cli-2.7 for this as well.

We should at some point generate the file based on other nvram
values.

Signed-off-by: Kumar Gala <[email protected]>