copy-on-write

[Chris Faylor]

I spent part of my "day off" today hacking together a "copy-on-write"
implementation for copying the heap after a fork.  I've long wanted to
try to do something like this.  It seems to work pretty well as long as
I don't fork something that forks something else.

I can't tell if there is a performance improvement or degradation or not
yet.

I hope that nobody is standing while reading this because I have some
shocking news.

The copy-on-write functionality is badly broken on Windows 95, so I
can't use it there.  This only works on NT.

cgf