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