Another case of DCE deleting live code

[Richard Kenner]

    I have to admit that TYPE_REF_CAN_ALIAS_ALL baffles me.  Sounds like an
    early hack and it's placed in the wrong spot.  A pointer does not really
    alias anything, it may *point* to other memory.  It is the pointed-to
    memory location that may *alias* other variables.

I added it, so I'll take any blame, but what the name means is that
the *reference* can alias all, which is exactly the semantics: we have
to assume that pointer can refeference anything. It's the exact opposite
of restricted pointers.