Hello.

After a discussion with Richi, using adding "-O2" to STAGE1 cflags with a recent
enough compiler can significantly speed up bootstrap. Thus I'm suggesting to
introduce --with-stage1-cflags where one can provide such options.

Apart from that, maybe it would be handy to automatically enable "-O2" when
one has a recent compiler? Do we have an example where we detect host compiler
and it's version?

Martin