Change of version of autoconf to version 2.63

[Sylvestre Ledru]

Hello,

For those who are using --enable-maintainer-mode and touchy to m4 macros
or the configure, we changed the version of autoconf from version 2.61
=> 2.63.
Please update you version (otherwise, it is changing all Makefile.in).

For Ubuntu:
http://mirrors.kernel.org/ubuntu/pool/main/a/autoconf/autoconf_2.63-2ubuntu1_all.deb
It going to be the default version of autoconf in the future ubuntu
(Jaunty).

For Debian: 
It is available in testing and can be easily installed on a stable
version.

Sylvestre