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

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

Merge jmallett@'s n64 work into HEAD - changeset 2

Update libc Makefiles.
Add makecontext implementation.

Changes from http://svn.freebsd.org/base/user/jmallett/octeon

Approved by: rrs(mentor), jmallett

Add mips support libc from the mips2-jnpr branch of perforce.