Remaining host configuration fragments

[DJ Delorie]

> But with this method, the hosts and targets we deprecate will probably be
> bitrotten anyway.  Without having machines or simulators for every
> supported host and target, we can't meaningfully have a state of
> deprecated but supported which means anything much.

We can tailor the message suitably.  What I'm saying is that before we
*actively* remove a host/target (regardless of the reason), we should
warn everyone.  This is different than trying to deduce which targets
have bitrotted that we otherwise don't know about.

In this case, Zack is (was?) removing files needed for irix5, without
advance warning.  Regardless of how bitrotted irix5 is, we should give
the users fair warning.