checl for the idn_free stuff to remain functionall even with older libidn

versions

configure.ac

@@ -963,6 +963,9 @@ case "$LIBIDN" in
                     ])
        if test "x$nolibidn" != "xtrue"; then
          curl_idn_msg="enabled"
+         dnl different versions of libidn have different setups of these:
+         AC_CHECK_FUNCS( idn_free )
+         AC_CHECK_HEADERS( idn-free.h )
        fi
                     
        ;;