Autoconf:
If you modify configure.ac or configure doesn't exist (eg if you checked
-the code out of CVS yourself) then you will need autoconf-2.60 to rebuild
-the automatically generated files by running "autoreconf".
+the code out of CVS yourself) then you will need autoconf-2.61 to rebuild
+the automatically generated files by running "autoreconf". Earlier
+version may also work but this is not guaranteed.
http://www.gnu.org/software/autoconf/