Point to regdef.h. May need to dig up references to the N32 standard
that support this usage (which may be a bit rough, since different
parts of the standard say mutually contradictory things).
Fix build after r249543.
Adapt libstand's setjmp/longjmp MIPS support to be portable across 32-bit
and 64-bit MIPS.  Don't use the floating-point coprocessor in the libstand
context for MIPS.

Reviewed by:	imp
MFC after:	3 days
Sponsored by:	DARPA, AFRL