Here's my implementation. I think somebody might have posted such a
thing to ruby-talk, but anyway this must have been written for the first
time by some Japanese Rubyist years ago, so yet another reinvention
won't matter nor hurt.
This definition of Class#include should be a
fairly safe replacement for the default one since I'm not raising an
exception when there's a nameclash (which I rather feel is a bad idea,
but I haven't given this much thought), but maybe it could make sense to
create a new method with those semantics.