carp: Add TSO and TXCSUM support

The carp's ifnet.if_hwassist is inheritted from the parent device.
carp: Increment output statistics properly
ethernet: Constify the lladdr pointer passed to ether_ifattach()
carp: Constify carp_etheraddr
carp: Prioritize carp advertisement packets
netrate/netperf: %.2f should be accurate enough
netrate/netperf: Record min/max results and calculate Jain's fairness index
route.8: Mention -msl, -iw and -iwmax
Merge branch 'master' into gsocdrm_alter