mdoc: remove superfluous paragraph macro.
Allow us to use the virtual timer. It is currently disabled, but should
be usable as the default timer in place of the physical timer.

We are guaranteed to have access to the virtual timer, but when running
under a hypervisor may not have access to the physical.

Differential Revision: https://reviews.freebsd.org/D588
Add OF_xref_from_node_strict() which returns -1 if there is no xref handle
for the node.  The default routine returns the untranslated handle, which
is sometimes useful, but sometimes you really need to know there's no
entry in the xref<->node<->device translation table.
Create a separate structure for per-CPU state saved across suspend and
resume that is a superset of a pcb.  Move the FPU state out of the pcb and
into this new structure.  As part of this, move the FPU resume code on
amd64 into a C function.  This allows resumectx() to still operate only on
a pcb and more closely mirrors the i386 code.

Reviewed by:	kib (earlier version)
Fix typo in comments.

Submitted by:	Benedict Reuschling <bcr@FreeBSD.org>
MFC after:	6 days
Add more bits for the XSAVE features from CPUID 0xd, sub-function 1
%eax report.

Print the XSAVE features 0xd/1 in the boot banner.  The printcpuinfo()
is executed late enough so that XSAVE is already enabled.

There is no known to me off the shelf hardware that implements any
feature bits except XSAVEOPT, the list is taken from SDM rev. 50.  The
banner printing will allow us to note the hardware arrival.

Sponsored by:	    The FreeBSD Foundation
MFC after:	    1 week