[m32c] type precedence rules and pointer signs

[DJ Delorie]

> The problem you are running into is that sizeof(sizetype) !=
> sizeof(void *).  In the middle-end the type used as offset
> (sizetype) doesn't have a defined signedness (it's unsigned for C,
> signed for Ada for example), so we rely on the fact that its size
> should match that of pointers (as then we don't need to worry about
> sign or zero extension).

That kind of assumption just isn't going to work for m32c, because
there aren't enough pointer-sized operators to satisfy gcc, so pointer
math has to be done in a smaller mode.  Doing it in a larger mode is
way too slow (all emulated math).

So... now what?