man pages for contrib programs

... would be really nice to have. Especially pgbench and pg_upgrade for
me, but it would be useful to have man pages for everything.

Unfortunately, we can't just replace the sect1's in in Appendix F [0]
with refentry's, because the content model of DocBook doesn't allow
that. (You can't have a mixed sequence of sect1 and refentry, only one
or the other.)

[0] http://www.postgresql.org/docs/devel/static/contrib.html

Which leads to a somewhat related point. The current content listing in
Appendix F mixes extensions (backend modules) with client and server
programs. Who can guess which is which here:

...
pg_archivecleanup
pgbench
pg_buffercache
pgcrypto
pg_freespacemap
pgrowlocks
pg_standby
pg_stat_statements
...

I think it would be useful to split this up into three sections:

F.1. Extensions
F.2. Client Applications
F.3. Server Applications

where the first looks like now and the other two contain the refentry
pages.

(This could also serve as a hint to packagers to split their -contrib
packages, so that say installing pgbench doesn't pull in a boatload of
other stuff.)

We could also consider making two separate appendixes. Maybe that would
result in a better table of contents.

Comments?