[v3] Library bits of c++/49813

[Paolo Carlini]

Hi,

> I ran into this problem on the IA64 HP-UX bootstrap and tried your
> patch to semantics.c.  It fixed the problem for me and I was able
> to bootstrap.

Thanks Steve. I say let's commit it, I'm pretty sure it's by and large correct and anyway it unbreaks the bootstrap for many people. Can you take care of that? I'm traveling and can only do it in a few hours.

Thanks,
Paolo