[RFC] Update to current automake/autoconf/libtool versions.

[Nathanael Nerode]

>I'd like to remind everyone involved that last I checked it was flat
>impossible to do what libstdc++-v3/configure.in needs to do, using
>autoconf 2.5x.  I am not particularly sanguine about the situation

Flat impossible?

Wow.

And for the top level, all I had to do was define my own entire set of
macros to replace the AC_CHECK_TOOL and AC_PROG_* collection. :-)

I'd be interested to hear more about the problem.  Why can't it be dealt 
with by using private macros?

--Nathanael