Added drivers for Hyper-V Synthetic Keyboard and Video device.

This change modifies the mainbus(4) entry point for all x86 sub-archs
in the following way:

i) It provides a unified entry point in
x86/x86/mainbus.c:mainbus_attach()
ii) It carves out the preliminary bus attachment sequence that is
common to all sub-archs into
x86/x86/mainbus.c: x86_cpubus_attach()
iii) It consolidates the remaining pathways as internal callee
functions so that these may be called piecemeal if required. A
special usecase of this is XEN PVHVM which may need to call the
native configure path, the xen configure path, or both.
iv) It moves the driver private data structures from
i386/i386_mainbus.c to an x86/ level one. This allows for other
sub-arch's to do similar, if needed. (They do not at the moment).
v) For dom0 kernels, it enables 'acpi0 at mainbus?' and
'acpi0 at hypervisorbus'. This serves two purposes:
a) To demonstrate the possibility of dynamic configuration tree
traversal ordering changes.
b) To allow for the common acpi_check(self, "acpibus") call in
x86/mainbus.c to not barf when it is called from the dom0 attach
path. We allow for the acpi0 device to be a child of mainbus with
the changes to amd64/conf/XEN3_DOM0 and i386/conf/XEN3PAE_DOM0
without actually probing further in the code. This path will later
be pursued in a PVHVM boot codepath.

There should be no operative changes with this change. If there are,
please complain loudly.

branches: 1.4.14;
Set hw.acpi.sleep.vbios when a non-HW accelerated VGA driver attaches.
If the VGA_POST option is present in the kernel the default value is 2,
otherwise 1. PR kern/50781

Reviewed by: agc, mrg

branches: 1.3.12; 1.3.30; 1.3.34;
Define some optional routines that will help device_register() to
register ISA & PCI devices. Add stub implementations of the routines.

Revert yesterday's change that attempted to fix the detection of the
boot device when using a Multiboot boot loader. It couldn't work because
these boot loaders do not pass a checksum of the disk so matchbiosdisk()
cannot really find any matches. I should have gone to sleep before
commiting...

Found by xtraeme@.

branches: 1.1.2;
When booting an i386 kernel with Multiboot, properly detect the boot device
by looking it up in the x86_alldisks table (instead of trying to match it
to 'wd*' manually).

In order to do this, move the cpu_rootconf function from x86 common code
to amd64 and i386 specific one. This way, i386 can do an extra step (call
the appropriate Multiboot code) in the appropriate place (after
x86_matchbiosdisks and before findroot()).

This change modifies the mainbus(4) entry point for all x86 sub-archs
in the following way:

i) It provides a unified entry point in
x86/x86/mainbus.c:mainbus_attach()
ii) It carves out the preliminary bus attachment sequence that is
common to all sub-archs into
x86/x86/mainbus.c: x86_cpubus_attach()
iii) It consolidates the remaining pathways as internal callee
functions so that these may be called piecemeal if required. A
special usecase of this is XEN PVHVM which may need to call the
native configure path, the xen configure path, or both.
iv) It moves the driver private data structures from
i386/i386_mainbus.c to an x86/ level one. This allows for other
sub-arch's to do similar, if needed. (They do not at the moment).
v) For dom0 kernels, it enables 'acpi0 at mainbus?' and
'acpi0 at hypervisorbus'. This serves two purposes:
a) To demonstrate the possibility of dynamic configuration tree
traversal ordering changes.
b) To allow for the common acpi_check(self, "acpibus") call in
x86/mainbus.c to not barf when it is called from the dom0 attach
path. We allow for the acpi0 device to be a child of mainbus with
the changes to amd64/conf/XEN3_DOM0 and i386/conf/XEN3PAE_DOM0
without actually probing further in the code. This path will later
be pursued in a PVHVM boot codepath.

There should be no operative changes with this change. If there are,
please complain loudly.

branches: 1.4.14;
Set hw.acpi.sleep.vbios when a non-HW accelerated VGA driver attaches.
If the VGA_POST option is present in the kernel the default value is 2,
otherwise 1. PR kern/50781

Reviewed by: agc, mrg

branches: 1.3.12; 1.3.30; 1.3.34;
Define some optional routines that will help device_register() to
register ISA & PCI devices. Add stub implementations of the routines.

Revert yesterday's change that attempted to fix the detection of the
boot device when using a Multiboot boot loader. It couldn't work because
these boot loaders do not pass a checksum of the disk so matchbiosdisk()
cannot really find any matches. I should have gone to sleep before
commiting...

Found by xtraeme@.

branches: 1.1.2;
When booting an i386 kernel with Multiboot, properly detect the boot device
by looking it up in the x86_alldisks table (instead of trying to match it
to 'wd*' manually).

In order to do this, move the cpu_rootconf function from x86 common code
to amd64 and i386 specific one. This way, i386 can do an extra step (call
the appropriate Multiboot code) in the appropriate place (after
x86_matchbiosdisks and before findroot()).

Set hw.acpi.sleep.vbios when a non-HW accelerated VGA driver attaches.
If the VGA_POST option is present in the kernel the default value is 2,
otherwise 1. PR kern/50781

Reviewed by: agc, mrg

branches: 1.3.30; 1.3.34;
Define some optional routines that will help device_register() to
register ISA & PCI devices. Add stub implementations of the routines.

Revert yesterday's change that attempted to fix the detection of the
boot device when using a Multiboot boot loader. It couldn't work because
these boot loaders do not pass a checksum of the disk so matchbiosdisk()
cannot really find any matches. I should have gone to sleep before
commiting...

Found by xtraeme@.

branches: 1.1.2;
When booting an i386 kernel with Multiboot, properly detect the boot device
by looking it up in the x86_alldisks table (instead of trying to match it
to 'wd*' manually).

In order to do this, move the cpu_rootconf function from x86 common code
to amd64 and i386 specific one. This way, i386 can do an extra step (call
the appropriate Multiboot code) in the appropriate place (after
x86_matchbiosdisks and before findroot()).