preparation for x86/acpica/acpi_wakeup.c

[Mitsuru IWASAKI]

Hi,

Well I think we are ready to have x86/acpica/acpi_wakeup.c to share
acpi_sleep_machdep() and acpi_wakeup_machdep() between amd64 and i386.

http://people.freebsd.org/~iwasaki/acpi/x86-acpi_wakeup-20120602.diff

There are no functional changes.  The following is major changes.
amd64:
- Add suspend/resume related members in PCB.
- Add suspendctx() in cpu_switch.S.
- acpi_switch.S moved into cpu_switch.S as resumectx().

amd64, i386:
- Add pcb_flags bit PCB_SUSPENDING to indicate AP is wakeup or not.


Please review the patches, suggestions welcome.
I'm going to commit this 1 week later.

Thanks