• dhcp method: run as 'up' not as 'pre_up', because we must
  set the interface to up to work
  (I still don't get an address…)
• lladdr plugin: new, use something like
  | auto eth0.1
  | iface eth0.1 inet dhcp
  |         switch-ports 0 5
  |         broadcast +
  |         lladdr 00:17:31:d6:9d:ae
  to use this (note: the format string is checked)
• main.sh: fix running of plugins
• Makefile: install lladdr plugin, bump dashver