Fix the build with gcc.
Axe ng_fec(4). It has never been a real netgraph(4) module, since
it had no hooks. It has abused ifnet's if_afdata slot and actually
abused every subsystem it touched.

lagg(4) is a proper trunking solution at ifnet(9) layer.

ng_one2many(4) is a proper trunking solution in netgraph(4).
ng_fec(4) removed.