Dependency tracking thought

[Tom Tromey]

gcc3 very nearly does exactly what automake wants in terms of
dependency tracking.

I think that ideally automake should recognize this and avoid using
depcomp when it discovers that the user is using gcc3.  In this
situation instead of invoking depcomp we would just invoke gcc like
depcomp does (with a small change):

    gcc <args> <dependency args> && mv "$tmpdepfile" "$depfile"

I don't think we need the explicit `rm $tmpdepfile' because the whole
problem is that gcc deletes it on failure.

Akim, any comments on the best approach to implementing this?
One problem I see is that detecting gcc3 in a language-independent way
is not going to be easy, at least not without autoconf assistance.

Tom