configure.in -> configure.ac

[Javier Jardón <javierjc1982 gmail com>]

Hi all,

As you probably know, the use of configure.in instead configure.ac
has been deprecated for long time.
Future versions of Automake will likely drop support for the
'configure.in' name for the Autoconf input file [1]

So if Its not already fixed in your module, we are going to proceed to
fix all the GNOME modules to avoid future breakages

Thanks for you collaboration.

[1] http://lists.gnu.org/archive/html/autotools-announce/2012-09/msg00000.html
-- 

Javier Jardón Cabezas