+# htmldir is not defined prior to autoconf 2.59c, so on earlier versions
+# set an equivalent value.
+AC_PREREQ([2.59c], [], [AC_SUBST([htmldir], [m4_ifset([AC_PACKAGE_TARNAME],
+ ['${datadir}/doc/${PACKAGE_TARNAME}'],
+ ['${datadir}/doc/${PACKAGE}'])
+])])