Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Include <sys/types.h> before <sys/systm.h> to get typedefs required
by new atomic.h. Fixes tinderbox LINT build.

Add a floating-point emulator so that a single userland or single ABI
can run on processors that don't have a FPU. This is typically the
case for Book E processors. While a tuned system will probably want
to use soft-float (or use a processor that has a FPU if the usage is
FP intensive enough), allowing hard-float on FPU-less systems gives
great portability and flexibility.

Obtained from: NetBSD