Add IP addressing + VLAN option to xcon (tap mode).
Add IP addressing + VLAN option to xcon (tap mode).

The new options allow configuration of VLAN ID, IPv4/6 address with
default gateway for the Tcp2Tap implementation.

plajjan/vrnetlab,mzagozen/vrnetlab,plajjan/vrnetlab,bdreisbach/vrnetlab,bdreisbach/vrnetlab,mzagozen/vrnetlab