Varargs issues

[James Van Artsdalen]

gcc will never generate code referencing memory at addresses less than
the current value of SP.  Is there much userland code that does this?
I'd almost rather let the signal handler trash these areas so such code
can be found and fixed.

I hope to get a Tyan K8W this week and to have it sufficiently
burned-in to boot amd64 next week.

> Plus there is another hairball to deal with.. the red zone..  The
> 128 bytes below the stack pointer are reserved for private use of
> leaf functions or scratch area.  This means that the signal handlers
> need to skip over it, and anything that copies the stack has to
> include the extra 128 bytes.