gnu_inline attribute for C++

[Jason Merrill]

Alexandre Oliva wrote:
>> And I'm still not clear why you check TREE_USED in the quoted code.
> 
> Just because that's how it was in the C front-end where I copied
> from.  As someone who's not an expert in any single front-end, but
> often finds oneself looking at problems in many of them, I thought
> such similarity might be welcome.  Assuming you prefer it differently,
> I took it out.

Thanks. I'm not sure why it would be there for C either, but it seems 
less dangerous for C.

OK to install.

Jason