Tunnel dev3

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