config: replace deprecated use of AC_OUTPUT with AC_CONFIG_FILES

Fix Automake warning: AC_OUTPUT should be used without arguments.
www.gnu.org/software/autoconf/manual/autoconf.html#Configuration-Files

Changed layout to one file per file like other xorg modules.

Signed-off-by: Gaetan Nadon <memsize@videotron.ca>
Reviewed-by: Arnaud Fontaine <arnau@debian.org>