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

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

Make kernel modules build correctly on 64-bit PowerPC.

Add the ofw_bus_if.h dependency introduced with r207585.

Add cas(4), a driver for Sun Cassini/Cassini+ and National Semiconductor
DP83065 Saturn Gigabit Ethernet controllers. These are the successors
of the Sun GEM controllers and still have a similar but extended transmit
logic. As such this driver is based on gem(4).
Thanks to marcel@ for providing a Sun Quad GigaSwift Ethernet UTP (QGE)
card which was vital for getting this driver to work on architectures
not using Open Firmware.

Approved by: re (kib)
MFC after: 2 weeks