Pull up following revision(s) (requested by ad in ticket #73):
sys/arch/amd64/amd64/fpu.c: revision 1.27
sys/arch/amd64/amd64/ipifuncs.c: revision 1.20
sys/arch/i386/i386/ipifuncs.c: revision 1.28
sys/arch/i386/isa/npx.c: revision 1.130
sys/arch/x86/include/intrdefs.h: revision 1.14
PR port-amd64/38293 panic: fp_save ipi didn't
Kill the FP flush IPI and always save. The synchronization here isn't
strong and we could easily pull the chain on an innocent LWP's FP state.
Another fix to follow.

(snj)