[RFA] Fix libsupc++/Makefile.in

[B. Kosnik]

> As a rule (which has been annoying me), automake tends to touch
> (recursively) any Makefile.in it finds.  What I usually do is to
> locate the Makefile.in I know should be regenerated and remove others
> that should not have been touched.  

when we are not in the middle of a release, let's come up with some
guidelines.

I think this has been an annoyance to all the maintainers for at least 6
months.

> Benjamin?

I'll do it Neil. Hang on.

-benjamin