Save and restore FPU state across suspend and resume.  In earlier revisions
of this patch, resumectx() called npxresume() directly, but that doesn't
work because resumectx() runs with a non-standard %cs selector.  Instead,
all of the FPU suspend/resume handling is done in C.

MFC after:	1 week
Replace cvsweb link wihg svnweb URL in bktr(4) release notes.