Warning for different pointer signedness

[Paul Schlie]

> Giovanni Bajo
> since your patch: http://gcc.gnu.org/ml/gcc-patches/2004-07/msg01284.html
> has a great impact on existing codebases (linux kernel guys say it triggers
> 6.5K times in full build), would you mind adding an entry about this into
> changes.html? It would help also to put a rationale there on why such a change
> was made, since we will undoubtly get this asked many times.

It would seem that the change was unnecessary, and possibly even incorrect,
as although the objects they referance are not of the same signedness,
their pointers (which are the objects being compared) are completely
compatible, as the storage size and alignment they reference is defined by
the objects storage class (i.e. char, short, int, long, etc.) which would
seem to be insensitive to the objects signedness, are equivalent.

 (although would expect a pedantic warning for (char *)cp == (int *)ip as
  pointers to dissimilar storage types may not have equivalent semantics)