* Provide some GNUisms as extensions.
* Provide dynamically growable string space.
* Make define(defn(foo)) work correctly for builtins.
(The current version is supposed to be capable of satisfying autoconf.)
All still relevant NetBSD changes have been preserved in this version, and
formatting and style fixes have been applied in various places.
Thanks to Masao Uebayashi <uebayasi@soum.co.jp> for pointing this out.
