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

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

For variables that are only checked with defined(), don't provide
any fake value.

bsd.doc.mk changes:

Don't gratuitously pipe thru a cat(1) if NODOCCOMPRESS.

Only create _stamp.extra when necessary.

Get rid of SOELIMPP and OBJS.

Use Groff version of soelim(1); we need its -I option
for the following to work.

Don't needlessly chdir to SRCDIR. Only a few documents
need CD_HACK, and those that need it either use refer(1)
or .PSPIC macro which internally uses the .psbb call.

Build this document in a standard way.

Correct build targets.

Make the documentation build.

This does not use the standard build macros for two reasons:

1. There's more than one document (paper and appendix).
2. The standard build macros need revision anyway (we shouldn't need
to set variables to get PostScript output, it should be a separate
target).

If anybody feels offended by this breach of style, feel free to fix
it.

Initial checkin: 4.4BSD version. These files need to be updated with
current license information and adapted to the FreeBSD build
environment before they will build.