Removal of support for GCC hosted on UWIN

[dewar@gnat.com]

<<Ditto Interix, IMO.
>>

I strongly disagree, Interix is entirely equivalent to Win32 from a logical
point of view, it is one of the alternative subsystems offered for use
with the NT kernel. When using NT, the operating system consists of
the kernel + a subsystem of your choice. Microsoft offers two possible
subsystems, Win32, and Interix. The combination of the NT kernel and
Interix provides a typical Unix like operating system. In no sense
is Interix a separate unit operating on top of Win32.

Part of the confusion here is that when people say NT, they usually
mean the combination of the NT kernel + the Win32 subsystem. If this
is your meaning when you use the term NT, then Interix is NOT a library
that runs under NT, it is an operating system in all the normal uses
of the term.