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

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

- change "is is" to "is" or "it is"
- change "the the" to "the"

Approved by: lstewart
Approved by: sahil (mentor)
MFC after: 3 days

Move most of the remaining USD/PSD/SMM papers into share/doc

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.

Eliminate groff(1) warnings.

Add Sun RPC documentation, which should eventually go into our PSD.
(I think I'm up to part 6.)