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

Return HAL_ANT_VARIABLE for now, until it's unstubbed.

This is needed by the slow antenna diversity logic for the AR9485/AR9462
as it's only engaged if the TX diveristy is set to VARIABLE.

Bring over my FreeBSD modifications for the AR9300 HAL to make it
work in FreeBSD.

This is still heavily a work in progress but I'd rather it start
shipping in -HEAD sooner rather than later.

This doesn't (yet) link it into the build system either for a static
kernel or as a module; that will come later (after many, many make universe
tests.)