Fix switchport trunk and related issues.

- in userspace use inverse logic bitmap (allowed vlans) while in "lisa.ko"
is kept a bitmap with forbidden vlans
- also fix bugs when matching the bitmap (do not print a vlan if not set as
allowed)
- free array of interfaces only if pointer not NULL (otherwise nasty segfault)
- tied up a little bit switch/lisa/lisa.c

Signed-off-by: Andreea Hodea <hodea_andreea@yahoo.com>