Eliminating usr/i686-pc-cygwin

[Chris Faylor <cgf at cygnus dot com>]

I've been perfecting my "mknetrel" script to the point where it is now
easy to eliminate the i686-pc-cygwin directory.

We've talked about doing this in the past and even, I think, decided that
we would do this for the next net release but we never did this.

I'm ready to make a cygwin release but I'd like to also make this change.

I can think of a few ways to do this.

1) Setup.exe can issue a warning if it sees this directory, and do nothing.

2) Setup.exe can issue a warning, and move the directory out of the way.

3) Setup.exe can issue a warning, and remove the directory.

4) Setup.exe can do 2) or 3) and do a:  'ln -s usr i686-pc-cygwin'.

I'm probably partial to 2.

The rationale for doing this is that some (broken?) configurators look
in /usr/include for specific header files and get confused when they
don't find anything there.

This will probably cause some pain in the short run but I think it is
worth it to make things look more like a normal UNIX system.

Thoughts?

cgf