New netlink library

New netlink library

To support netlink and IP address processing, two new library files were
added:

netlink: Generic netlink message processing code converting netlink
messages to calls of callbacks with a pre-processed data.

netaddrq: A code that gets and maintains linked list of the current
interfaces and assigned IP addresses. It also provides a rating of IP
addresses based on its "quality", i. e. type of address, validity, lifetime
etc.

Signed-off-by: Stanislav Brabec <sbrabec@suse.cz>