(toplevel) introduce host subdir configuration in Makefile

[Andrew Cagney]

>>>[...] This particular bit is likely to be the most destabilizing of my 
>>>changes; most of the stuff prior to it was carefully
>>> designed to be "behavior-change-free".
> 
>> Yes, that's why I'd like to see it sooner rather than later. Plenty of 
>>time before 5.4/6.0 branches to fix problems.
>>
>> Andrew
> 
> And when is that branch anticipated to happen?  (So I can plan...)

Honestly, who knows.  Febuary, march, april?

A GDB branch isn't that much of a deal.

Andrew