[Bridge + 8021q] Implementation of "if_add_trunk_vlans" and "if_set_trunk_vlans"
* interfaces that are reffered by if_data structures contain a field allowed_vlans witch is a shared structure pointer to a unsigned char * bitmap that holds the vlans in positive logic
* adding and setting vlans are persistent. If you are in access mode and you set some trunk vlans to the interface these changes will be accesible when the interface is moved in trunk mode.
Signed-off-by: Victor Duta <duta.victor.marin@gmail.com>