Thanks to you all for the help!

I'm installing the following patch on Autoconf (I have left its side
effects, such as on configure, so that people can look at its impact).
Feel free to fix my words about Zsh.

Allen, I'll wrap a tarball, once the test suite finished (err... a
couple of hours I guess), will you be able to re-run the test suite on
that tarball?  I expect much less than 126 failures on 163 tests :)