bug#23640: 25.1.50; Getting rid of compiler warnings

[Paul Eggert]

Richard Stallman wrote:
> I guess so -- but is it a noticeable slowdown?  A priori, I doubt it.

You're probably right. The major effect these days would be on cache pressure, 
which is tricky to measure.

> If it is not significant, why worry about it?
> Better to write the code in the clean way.

For me it's cleaner to think of UNINIT as an attribute for a declaration, 
instead of thinking of UNUSED as a special expression that neither transfers 
control nor has a side effect nor yields a value. It's merely a plus that UNINIT 
generates code that is a tiny bit smaller and faster.