[patch mingw]: Adds for mingw targets the EH thread code to libgcc

[Dave Korn]

Kai Tietz wrote:

> I tested this patch for i686-pc-cygwin and for i686-pc-mingw32 (by 
> mingw.org's runtime).

> Is this patch ok for apply, or are there any further suggestions, or any 
> objectives?

  No objections.  I think that:

>         * gthr-win32.h (MINGW32_SUPPORTS_MT_EH): Define
>         it for targets defining _WIN32 but not __CYGWIN__.

... you don't really need to worry too much about this angle.  We don't
support win32 threads on Cygwin, only --enable-threads=posix is important to us.

    cheers,
      DaveK