ACPI mpsafe patch

[Nate Lawson]

I've gone through this carefully and have tested it a lot and it appears
ready for mainstream testing.  I'm especially interested in SMP testing,
with and without WITNESS.  Run the following script on your system to test
it (start 2 or 3 of these):

#!/bin/sh
sysctl hw.acpi.thermal.polling_rate=1
sysctl hw.acpi.battery.info_expire=1
while [ 1 ]; do
	apm
	sysctl hw.acpi
done

While that's going, use the system normally, suspend/resume, etc.

The few parts that aren't done are acpi_video, acpi_asus, and
acpi_toshiba.  Once I finish these and a couple nits, I'll provide a final
patch for testing as well as fix any problems found.

    http://www.root.org/~nate/freebsd/acpi_mpsafe.diff.gz

Thanks,
-Nate