More C type errors by default for GCC 14

[Florian Weimer]

* Florian Weimer:

> In summary, all these seems to be good candidates for errors by default:
>
> * int-conversion as errors (already raised separately
> * -Wint-conversion for ?:
> * parameter names in non-prototype function declarations
> * the union wait function pointer compatibility kludge
> * return-with-out-value for non-void functions
> * -Wincomatible-pointer-types warning for ?: (but no error yet, see below)

I think we have another problem.

We do not warn by default for:

  int x;
  unsigned *p;

  p = &x;

Isn't that a conformance issue because the pointers are incompatible,
requiring a diagnostic?

Furthermore, Unlike the char case, this tends to introduce
strict-aliasing violations, so there is a good reason to treat this
variant as an error (even if we would only warn for char * and
unsigned char *).