Updating top-level autoconf to 2.59

[Maciej W. Rozycki]

On Fri, 9 Feb 2007, Daniel Jacobowitz wrote:

> Here is what I have checked in.  I had to duplicate a bit of a patch
> from Paul in 2005, to work around an autoconf bug (already fixed
> upstream): AC_PATH_PROG mangles IFS if the supplied path is empty.
> That showed up when I tested in src without GCC.

 Could using autoconf 2.61 have helped?

  Maciej