[PATCH] Fix optimization regression in constant folder

[Richard Kenner]

> Exactly.  This type should not be produced or used by anything else than 
> Ada.

Huh?  sizetype has nothing whatsoever to do with Ada or any other language.
It's the type that we use for the trees in TYPE_SIZE, TYPE_SIZE_UNIT,
DECL_SIZE, DECL_SIZE_UNIT, DECL_FIELD_OFFSET, the component size in an
ARRAY_REF and the offset in a COMPONENT_REF.