build: require at least 2-year old autoconf-2.64 (was 2.62)

* configure.ac: Require autoconf-2.64, which is nearly two years old.
* src/system.h (emit_ancillary_info): Use PACKAGE_URL, now that we
require autoconf-2.64.

configure.ac

@@ -18,7 +18,7 @@
 
 dnl Written by Jim Meyering.
 
-AC_PREREQ([2.62])
+AC_PREREQ([2.64])
 
 # Make inter-release version strings look like, e.g., v6.9-219-g58ddd, which
 # indicates that it is built from the 219th delta (in _some_ repository)

src/system.h

@@ -593,9 +593,7 @@ emit_ancillary_info (void)
 {
   printf (_("\nReport %s bugs to %s\n"), last_component (program_name),
           PACKAGE_BUGREPORT);
-  /* FIXME 2010: use AC_PACKAGE_URL once we require autoconf-2.64 */
-  printf (_("%s home page: <http://www.gnu.org/software/%s/>\n"),
-          PACKAGE_NAME, PACKAGE);
+  printf (_("%s home page: <%s>\n"), PACKAGE_NAME, PACKAGE_URL);
   fputs (_("General help using GNU software: <http://www.gnu.org/gethelp/>\n"),
          stdout);
   /* Don't output this redundant message for English locales.