[Bug tree-optimization/16705] ICE in verify_flow_insensitive_alias_info

[Richard Kenner]

    This patches fixes this problem.  Essentially, we should always consider
    .GLOBAL_VAR as potentially aliased.  This may have been related to the
    Ada bootstrap problems.  Kenner, could you check?  Thanks.

It fixes the file I saw fail.  I started another bootstrap; if something else
turns up that looks related, I'll let you know.  I figured it was something
simple like this, but wasn't sure exactly what.

Thanks.