> 
> I'd like to commit this sometime tonight or tomorrow, and then feed back 
> to FSF.
> 
> Any suggested improvements before I do so?

The idea for the patch looks good, though I'm not sure it even needs to
be an option IMO, but others may care more about that.

Couple of comments:

1) Whitespace. For the diff for the FSF you'll want to use unified (as I
mentioned before) and probably use -w since you appear to have a lot of
whitespace changes. Also, you'll only need to send patches for non-
generated files at that point.

2) Word of warning: Mainline has changed a bit. cpp is now in it's own
top level directory.

3) Extra bits:

+   The `-isystem-cxx' command line option adds its argument to the list
+of C++ system headers, similar to `-isystem' for C headers.
+
You seem to have some various bits for -isystem-cxx in the patch...

Otherwise it looks good to me for FSF - not that it's an area I can approve
mind you :)

-eric