Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

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

MFC r227458, r226436:

- change "is is" to "is" or "it is"
- change "the the" to "the"
- other typo fixes

Approved by: lstewart

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

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

Correct typos, mostly s/ a / an / where appropriate. Some whitespace cleanup,
especially in troff files.

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.)