PATCH: Fix __WORDSIZE for ia64.

[Roland McGrath]

> With this change, the only loss is we can no longer access the old utmp
> file. I think it is the price we should pay to fix the problem. 

I am inclined to agree with this conclusion (the same one made on other
64/32 platforms).  But it's not a change you just slip in without comment,
discussion with users and system maintainers, and approval from the
architecture's canonical maintainer.