Fix up references to "PostgreSQL" rather than "Postgres". Was roughly
 evenly split between the two before. ref/ files not yet done.

Use --enable-nls to turn it on; see installation instructions for details.
See developer's guide how to make use of it in programs and how to add
translations.

psql sources have been almost fully prepared and an incomplete German
translation has been provided.  In the backend, only elog() calls are
currently translatable, and the provided German translation file is more
of a placeholder.