autoconf 2.67-2ubuntu1 (amd64 binary) in ubuntu natty

 The standard for FSF source packages. This is only useful if you
 write your own programs or if you extensively modify other people's
 programs.
 .
 For an extensive library of additional Autoconf macros, install the
 `autoconf-archive' package.
 .
 The Debian project regards the full documentation for autoconf to be
 non-free, so it is not included in Debian. Nevertheless, the
 non-free distribution that accompanies Debian includes the manual in
 its `autoconf-doc' package.
 .
 This version of autoconf is not compatible with scripts meant for
 Autoconf 2.13 or earlier. If you need support for such scripts,
 you must also install the autoconf2.13 package.