atomic accesses

[Florian Weimer]

* Segher Boessenkool:

> Good point.  Suggestions for better wording?  How does
>
> 	"any access to a naturally aligned scalar object in memory
> 	that is not a bit-field and fits in a general purpose integer
> 	machine register, will be performed by a single machine
> 	instruction whenever possible"

Vectorization already breaks this promise, and so does dead store
elimination, at least if you interpret "single" as "exactly one".
"At most one" could be a better choice.