Use our actual autoconf and automake versions to unbreak build when
autoconf-2.63 is installed but automake-1.11 is not.

Index: autogen.sh
--- autogen.sh.orig
+++ autogen.sh
@@ -17,8 +17,8 @@
 # Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
 # USA.
 
-AM_VERSION=1.11
-AC_VERSION=2.63
+AM_VERSION=${AUTOMAKE_VERSION}
+AC_VERSION=${AUTOCONF_VERSION}
 
 run_versioned() {
     local P