Add includes to interfaces.inc

There were some includes needed when calling into here from rc.linkup - somehow everything else that calls interface_configure(p1, "true", p3) has already included these.
Reload routes etc when rc.linkup happens

When a link comes up, call interface_configure with p2=true. This makes it run various extra routines such as system_routing_configure - which will put back the default route or other static routes that might have been removed when the link was down.
Merge pull request #626 from phil-davis/master

Restore default route after HOTPLUG linkup