Removal of support for GCC hosted on UWIN

[Mark Mitchell]

We've learned that the usage of GCC on U/WIN involves a violation of
the GNU GPL, linking GCC with a non-free third-party support library;
therefore, we have removed the support for such usage.

Note that GCC is merely a special case: it is a violation of the GPL
to link *any* GPL'd program with the U/WIN support library.

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Mark Mitchell                   mark@codesourcery.com
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