Removal of support for GCC hosted on UWIN

[dewar@gnat.com]

<<So how does a binary that links (say) HPUX's libc.sl, or Sun's libc.so
get allowed?
>>

Well I guess the answer is RTFL (L = license). There is a clear
distinction made in the last paragraph but one of section 3 that
obviously applies to the examples you cite here:

------
However, as a
special exception, the source code distributed need not include
anything that is normally distributed (in either source or binary
form) with the major components (compiler, kernel, and so on) of the
operating system on which the executable runs, unless that component
itself accompanies the executable.