"unable to detect exception model"

[Benjamin Kosnik]

> I think that in the meanwhile (waiting for the new eh in the branch) I will
> try the "frankenstein-ish" move: I *must* understand if the cin problem I'm
> experiencing with recent Gcc3.1 snapshots is newer-libstdc++-proper-related,
> new eh-related, or what!

I'm on your cin bug, it has to do with my recent changes to sync_with_stdio.
Hang on, I'm working on it.

-benjamin