Tunnel dev3

1. Got rid of ifla_map - it's original goal was to not have to mess with IFLA_IPTUN vs. IFLA_GRE in places like iflist.c. I'm happy with or without it.

2. For sit tunnels, added reading if iflags to determine 'isatap'. Hence, there will be no need to add a NI_IFTYPE_ISATAP.