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

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

Make the existing ath tools build again.

* add missing includes to quieten warnings
* fix an inline function decl to have a return type
* since .h files are created during the build (opt_ah.h, ah_osdep.h)
which modify the behaviour of the HAL include/source files,
include OBJDIR in the path so the #include's work.

The tools should now build when the directory is added to LOCAL_DIRS
during a make buildworld.

bring in diagnostic tools that are useful now that we have hal source code