Updating top-level autoconf to 2.59

[DJ Delorie]

erik@dd.nec.com.au (Erik Christiansen) writes:
> --build seems to be a synonym for --host,

Not at all.  To recap:

--build is the machine running the build

--host is the machine the resulting programs will run on

--target is the machine those programs generate code for

So, for example, if I wanted to use my linux box to build a gcc.exe
that runs on cygwin and produces m32c programs:

./configure --build=linux --host=cygwin --target=m32c

(names are abbreviations, of course)