Define PACKAGE_URL for older autoconf.

autoconf < 2.64 doesn't define PACKAGE_URL through AC_INIT.
Define it ourselves if needed.

Signed-off-by: Mark Wielaard <mark@klomp.org>
diff --git a/ChangeLog b/ChangeLog
index bb2ec10..a587b43 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2017-01-12  Mark Wielaard  <mark@klomp.org>
+
+	* configure.ac: Define PACKAGE_URL for older autoconf.
+
 2016-12-27  Mark Wielaard  <mark@klomp.org>
 
 	* configure.ac: Set version to 0.168.
diff --git a/configure.ac b/configure.ac
index 4549906..07ad592 100644
--- a/configure.ac
+++ b/configure.ac
@@ -19,6 +19,12 @@
 dnl  along with this program.  If not, see <http://www.gnu.org/licenses/>.
 AC_INIT([elfutils],[0.168],[https://sourceware.org/bugzilla],[elfutils],[http://elfutils.org/])
 
+dnl Workaround for older autoconf < 2.64
+m4_ifndef([AC_PACKAGE_URL],
+         [AC_DEFINE([PACKAGE_URL], ["http://elfutils.org/"],
+                    [Define to home page for this package])
+          AC_SUBST([PACKAGE_URL], ["http://elfutils.org/"])])
+
 # We want eu- as default program prefix if none was given by the user.
 # But if the user explicitly provided --program-prefix="" then pretend
 # it wasn't set at all (NONE). We want to test this really early before