[tree-ssa] Fix variables getting out of their scope

[Richard Henderson]

> Though one could argue that at least for the replace_stmt case that
> using a BIND_EXPR is really just avoiding rewriting the equivalent of
> rationalize_compound_expr which preserves/updates basic block information.

Well, yes, I am going to argue that.  ;-)

It is something that would need to get fixed, possibly before
starting on the rest of the code to excise BIND_EXPR.



r~