Optimizing of explicit temporary storage

[Florian Weimer]

* Mark Mitchell:

> I don't think any compiler has ever attempted to turn:
>
>  free (malloc (16));
>
> into a no-op, which would be a simpler case.

There are scheme compilers that turn heap allocation into stack
allocation if they can prove that the object does not escape.
Java code would benefit from this optimization, too.