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

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

Improve cpu_idle():
o cpu_idle_hook is expected to be called with interrupts
disabled and re-enables interrupts on return.
o sync with x86: don't idle when the CPU has runnable tasks
o have callers of ia64_call_pal_static() disable interrupts
and re-enable interrupts.
o add, but compile-out, support for idle mode. This will be
enabled at some later time, after proper testing.

Add acpi_find_table() -- a convenience function for looking up an
ACPI table given the signature.

Import ACPICA 20090521.

Canonize the include of acpi.h.

Move the code for halting the CPU (acpi_cpu_c1) into machdep files.
This removes the last MD portion of acpi_cpu.c.

MFC after: 2 weeks

Add machdep quirks functions. On i386, this disables acpi on systems with
BIOS dates earlier than Jan 1, 1999. Add prototypes and quirks flags.

Don't check for NULL, device_get_softc() always succeeds.

Minor style cleanups.

Add APM compatibility feature to ACPI.
This emulates APM device node interface APIs (mainly ioctl) and
provides APM services for the applications. The goal is to support
most of APM applications without any changes.
Implemented ioctls in this commit are:
- APMIO_SUSPEND (mapped ACPI S3 as default but changable by sysctl)
- APMIO_STANDBY (mapped ACPI S1 as default but changable by sysctl)
- APMIO_GETINFO and APMIO_GETINFO_OLD
- APMIO_GETPWSTATUS

With above, many APM applications which get batteries, ac-line
info. and transition the system into suspend/standby mode (such as
wmapm, xbatt) should work with ACPI enabled kernel (if ACPI works well :-)

Reviewed by: arch@, audit@ and some guys