LT_PREREQ breaks autoreconf

[Jason Curl]

I have a macro and in the first lines are:

AC_PREREQ(2.61)
LT_PREREQ([2.2.6])

When I run "autoreconf" I get:
$ autoreconf
configure.ac:33: error: m4_defn: undefined macro: _m4_divert_diversion
configure.ac:33: the top level
autom4te-2.63: /usr/bin/m4 failed with exit status: 1
aclocal-1.10: autom4te failed with exit status: 1
autoreconf-2.63: aclocal failed with exit status: 1

If I remove "LT_PREREQ" then the configure script compiles and I can 
move forward.

But now that I've updated my CVS tree for libtool 2.2.6 I want an error 
if I run autoreconf with a system that still has 1.5.x installed (to say 
I can't support that anymore). And according to the libtool manual this 
should work, but it doesn't for me.

Help much appreciated.
Jason.



Details about my system:
$ autoconf --version
autoconf (GNU Autoconf) 2.63
Copyright (C) 2008 Free Software Foundation, Inc.
License GPLv2+: GNU GPL version 2 or later
<http://gnu.org/licenses/old-licenses/gpl-2.0.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Written by David J. MacKenzie and Akim Demaille.

$ uname -a
CYGWIN_NT-5.1 europa 1.5.25(0.156/4/2) 2008-06-12 19:34 i686 Cygwin

$ libtool --version
ltmain.sh (GNU libtool) 2.2.6
Written by Gordon Matzigkeit <address@hidden>, 1996

Copyright (C) 2008 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ automake --version
automake (GNU automake) 1.10.1
Copyright (C) 2008 Free Software Foundation, Inc.
License GPLv2+: GNU GPL version 2 or later 
<http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Written by Tom Tromey <address@hidden>
      and Alexandre Duret-Lutz <address@hidden>.