Patch: stab info for const fields

[Richard Kenner]

     (3a) The types are "compatible", which is a term with a precise
          but language-specific definition; consult the relevant standard.

I don't like that idea at all.  It means that how you interpret a tree
in the middle-end is a function of the front-end that generated it.
But I'd strongly argue that the trees are meant to be a
language-independent IL.