aliasing warnings [patch]

[Jeffrey A Law]

  In message < 199909240006.RAA28376@atrus.synopsys.com >you write:
  > Someone mentioned that DEC's compiler issues warnings of this type
  > and that's how the Perl team became aware of the issue.  The above
  > approach seems like a clean way to get such warnings, for the case
  > where all the code is in the same function.
  > 
  > The RMS variant (sure to be contoversial) would be to put a pointer with
  > this tag into alias set 0 (it can alias everything).
I haven't thought a lot about the implications of this, but at first glance
it's not a bad idea.

It should achieve RMS's goal of having old broken code still work without a
severe impact on most conforming code.

It's behavior should be consistent over time and we should be able to
document the behavior.

I don't know how difficult this is from a technical standpoint, but it is
probably worth some investigation.

jef