instead of prepending; this is for consistency with other GNU tools.
The new -B DIR or --prepend-include=DIR option has the old behavior.
-- When configured with the new --enable-site-macro-dir=DIR configure-time
- option, Autoconf now appends DIR to the default include path.
+- Autoconf now normally appends ${datadir}/autoconf/site_macros to the
+ include path. The new --disable-site-macro-dir configure-time
+ option inhibits this, and the new --enable-site-macro-dir=DIR
+ configure-time option causes it to append DIR instead.
** Macros