IPv6 support for virtual_routes and static_routes

This patch is based on work done by Robert Sander, <gurubert <at> gurubert <dot> de>.
I reworked it a little bit in some places to provide better inclusion. So please,
Robert, if you read those line give it a read as a double check.

This patchset add support to generic ip address handling in vrrp route framework. You
can now use IPv4 as well as IPv6 addresses in vrrp virtual routes or static routes
configurations.