Update touchconfig.sh for renamed configure.in -> configure.ac

touchconfig.sh

@@ -4,5 +4,5 @@
 # and insists they need to be regenerated, though they really don't.
 # This script bumps the timestamps on the right files in the right order,
 # such that they don't all match, and make can proceed on its way.
-touch configure.in acinclude.m4 aclocal.m4 configure Makefile.am Makefile.in
+touch configure.ac acinclude.m4 aclocal.m4 configure Makefile.am Makefile.in