Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

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

MFC: r231787

Make ACPI resume beeper less cryptic. Set PIC timer2 mode properly.

MFC: r230830

Restore XCR0 before restoring extended FPU states.

MFC: r230777

Naturally align a newly added wakeup_fpusave.

MFC r230426:
Add support for the extended FPU states on amd64, both for native
64bit and 32bit ABIs. As a side-effect, it enables AVX on capable
CPUs.

MFC r230765:
Synchronize the struct sigcontext definitions on x86 with mcontext_t.

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Reinitialize PAT MSR via pmap_init_pat() while resuming. This function does
better job since r215703 and it is safer now.

savectx() has not been used for fork(2) for about 15 years. [1]
Do not clobber FPU thread's PCB as it is more harmful. When we resume CPU,
unconditionally reload FPU state.

Pointed out by: bde [1]

- Merge savectx2() with savectx() and struct xpcb with struct pcb. [1]
savectx() is only used for panic dump (dumppcb) and kdb (stoppcbs). Thus,
saving additional information does not hurt and it may be even beneficial.
Unfortunately, struct pcb has grown larger to accommodate more data.
Move 512-byte long pcb_user_save to the end of struct pcb while I am here.
- savectx() now saves FPU state unconditionally and copy it to the PCB of
FPU thread if necessary. This gives panic dump and kdb a chance to take
a look at the current FPU state even if the FPU is "supposedly" not used.
- Resuming CPU now unconditionally reinitializes FPU. If the saved FPU
state was irrelevant, it could be in an unknown state.

Suggested by: bde [1]

Move i386-inherited logic of building ACPI headers for acpi_wakeup.c into
better places and remove intermediate makefile and shell scripts. This
makes parallel kernel build little bit safer for amd64.

Try hiding annoying text cursor after the video controller is reset.

Clean up amd64 suspend/resume code.

- Allocate memory for wakeup code after ACPI bus is attached. The early
memory allocation hack was inherited from i386 but amd64 does not need it.
- Exclude real mode IVT and BDA explicitly. Improve comments about memory
allocation and reason for the exclusions. It is a no-op in reality, though.
- Remove an unnecessary CLD from wakeup code and re-align.

Chase GDT layout changes and unbreak suspend/resume on amd64.

- Clean up suspend/resume code for amd64.
- Call acpi_resync_clock() to reset system time before hardclock is ready
to tick. Note we assume the current timecounter hardware and RTC are
already available for read operation.

Tested by: mav

Initial suspend/resume support for amd64.

This code is heavily inspired by Takanori Watanabe's experimental SMP patch
for i386 and large portion was shamelessly cut and pasted from Peter Wemm's
AP boot code.