Problem in locate_and_pad_parm

[Richard Kenner]

    Actually, there was a change.  MUST_PASS_IN_STACK can now be overridden
    in the tm.h file, and some targets actually do this today.

That's incorrect and should be removed!

MUST_PASS_IN_STACK is a macro that's meant to represent those cases
where GCC does not know to pass parameters in registers.  It should *never*
be overriden.  Instead, the underlying macros should be changed in
the ports in question.

This is now defined in *a lot* ports.  Each needs to be fixed.

Didn't we discuss this a while ago?