Autoconf versions

I notice that some of the people committing configure fixes are using
autoconf 2.13 while some are still on 2.12.  This is a Bad Thing ---
it's not only generating huge diffs at each commit, but we don't know
which script version we've got day to day.

We need to standardize what version is being used.  2.13 is probably
the right choice, unless anyone knows of serious bugs in it.  (I'm
still on 2.12 myself but am willing to upgrade.)

An alternative possibility is to stop keeping configure in the CVS
repository, but that would mean expecting everyone who uses the CVS
sources to have autoconf installed ... I suspect that's a bad idea.
        regards, tom lane