This allows it to be used on Windows without installing mingw
(though you do still need 'diff'), and opens the door to future
improvements such as message localization.
Magnus Hagander and Tom Lane.

code to forcibly drop regressuser[1-4] and regressgroup[1-2].  Instead,
let the privileges.sql test do that for itself (this is made easy by
the recent addition of DROP ROLE IF EXISTS).  Per a recent patch proposed
by Joachim Wieland --- the rest of his patch is superseded by the
rewrite into C, but this is a good idea we should adopt.

setting for the regression makefile, allowing Windows users to force locale
settings since Windows does not get its locale from the environment.

Per Petr Jelinek.

as per my recent proposal.  For now the template data is hard-wired in
proclang.c --- this should be replaced later by a new shared system
catalog, but we don't want to force initdb during 8.1 beta.  This change
lets us cleanly load existing dump files even if they contain outright
wrong information about a PL's support functions, such as a wrong path
to the shared library or a missing validator function.  Also, we can
revert the recent kluges to make pg_dump dump PL support functions that
are stored in pg_catalog.
While at it, I removed the code in pg_regress that replaced $libdir
with a hardcoded path for temporary installations.  This is no longer
needed given our support for relocatable installations.

port number, and use a default value for it that is dependent on the
configuration-time DEF_PGPORT.  Should make the world safe for running
parallel 'make check' in different branches.  Back-patch as far as 7.4
so that this actually is useful.

CREATE DATABASE does one internally.

unlike template0 and template1 does not have any special status in
terms of backend functionality.  However, all external utilities such
as createuser and createdb now connect to "postgres" instead of
template1, and the documentation is changed to encourage people to use
"postgres" instead of template1 as a play area.  This should fix some
longstanding gotchas involving unexpected propagation of database
objects by createdb (when you used template1 without understanding
the implications), as well as ameliorating the problem that CREATE
DATABASE is unhappy if anyone else is connected to template1.
Patch by Dave Page, minor editing by Tom Lane.  All per recent
pghackers discussions.