l4linux: Add internal NIC driver

Fix l4linux and l4lx library build script for build l4linux with user
configs.
Add l4linux driver which is implemented the NIC service and it can be
used for connect two l4linux instances using the NIC interface.
Extend l4linux net driver for using several NIC services.
Add a few run scrips for tests.
Add label parameter to Nic session for using if-arg mechanism in session
routing.
Merge branch 'l4linux-net' of github.com:Ksys-labs/genode into l4linux-net

Conflicts:
	iloskutov/run/l4linux2.run