Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

- There's no need to overwrite the default device method with the default
one. Interestingly, these are actually the default for quite some time
(bus_generic_driver_added(9) since r52045 and bus_generic_print_child(9)
since r52045) but even recently added device drivers do this unnecessarily.
Discussed with: jhb, marcel
- While at it, use DEVMETHOD_END.
Discussed with: jhb
- Also while at it, use __FBSDID.

Add the sfxge(4) device driver, providing support for 10Gb Ethernet adapters
based on Solarflare SFC9000 family controllers. The driver supports jumbo
frames, transmit/receive checksum offload, TCP Segmentation Offload (TSO),
Large Receive Offload (LRO), VLAN checksum offload, VLAN TSO, and Receive Side
Scaling (RSS) using MSI-X interrupts.

This work was sponsored by Solarflare Communications, Inc.

My sincere thanks to Ben Hutchings for doing a lot of the hard work!

Sponsored by: Solarflare Communications, Inc.
MFC after: 3 weeks