Autoconf 2.69 update

I'm proposing that we upgrade our Autoconf to 2.69, which is the latest
right now (release date 2012-04-24). There are no changes in the source
needed, just tweak the version number in configure.in (see below) and
run autoreconf. I've compared the configure output before and after on
a few boxes, and there were no significant changes.

The major benefit of this update is that configure shrinks to about half
the size and also runs a bit faster.

Maybe at this time, everyone who is interested can check that they have
an installation of Autoconf 2.69 around, and then in a few weeks we can
do the update.

diff --git a/configure.in b/configure.in
index a4baeaf..ac61be5 100644
--- a/configure.in
+++ b/configure.in
@@ -19,7 +19,7 @@ m4_pattern_forbid(^PGAC_)dnl to catch undefined macros

AC_INIT([PostgreSQL], [9.4devel], [pgsql-bugs(at)postgresql(dot)org])

-m4_if(m4_defn([m4_PACKAGE_VERSION]), [2.63], [], [m4_fatal([Autoconf version 2.63 is required.
+m4_if(m4_defn([m4_PACKAGE_VERSION]), [2.69], [], [m4_fatal([Autoconf version 2.69 is required.
Untested combinations of 'autoconf' and PostgreSQL versions are not
recommended. You can remove the check from 'configure.in' but it is then
your responsibility whether the result works or not.])])