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

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

Fix build with gcc. Move sf_buf_alloc()/sf_buf_free() declarations
to MD headers.

On those machines, where sf_bufs do not represent any real object, make
sf_buf_alloc()/sf_buf_free() inlines, to save two calls to an absolutely
empty functions.

Reviewed by: alc, kib, scottl
Sponsored by: Nginx, Inc.
Sponsored by: Netflix

Implement sf_buf using direct map (XKPHYS) in MIPS n64.

- Provide trivial implementation of sf_buf_alloc(), sf_buf_free(),
sf_buf_kva() and sf_buf_page() using direct map for n64.
- uio_machdep.c - use macros so that the direct map will be used in
case of n64.

Reviewed by: imp (earlier version)
Obtained from: jmallett (user/jmallett/octeon)

o) Use the direct map where possible for uiomove_fromphys, based on code from
sparc64.
o) Use uiomove_fromphys rather than the broken fpage mechanism for /dev/mem.
o) Update sf_buf allocator to not share buffers and to do a pmap_qremove when
done with an sf_buf so as to better track valid mappings.

Set the svn:eol-style = native and svn:mime-type = text/plain
properties on all files in this tree.

Submitted by: rpaulo@

FreeBSD/mips port. The FreeBSD/mips port targets mips32, mips64,
mips32r2 and mips64r2 (and close relatives) processors. There
presently is support for ADMtek ADM5120, A mips 4Kc in a malta board,
the RB533 routerboard (based on IDT RC32434) and some preliminary
support for sibtye/broadcom designs. Other hardware support will be
forthcomcing.

This port boots multiuser under gxemul emulating the malta board and
also bootstraps on the hardware whose support is forthcoming...

Oleksandr Tymoshenko, Wojciech Koszek, Warner Losh, Olivier Houchard,
Randall Stewert and others that have contributed to the mips2 and/or
mips2-jnpr perforce branches. Juniper contirbuted a generic mips port
late in the life cycle of the misp2 branch. Warner Losh merged the
mips2 and Juniper code bases, and others list above have worked for
the past several months to get to multiuser.

In addition, the mips2 work owe a debt to the trail blazing efforts of
the original mips branch in perforce done by Juli Mallett.