This fixes bootstrap issues with current mingw-w64 headers:

    ```
    ../../gcc/gcc/system.h:791:30: error: expected identifier before string constant
      791 | #define abort() fancy_abort (__FILE__, __LINE__, __FUNCTION__)
          |                              ^~~~~~~~
    ```


The changes in this commit were generated by the following command, with some post-processing:

    ```
    sed -Ei 's,^( *)#( *)include <windows\.h>,\1#\2define WIN32_LEAN_AND_MEAN\n&,'  \
      $(grep -Flr "<windows.h>")
    ```


This has been tested with C, C++, LTO, Fortran, Objective-C, Objective-C++ and JIT, on 
{i868,x86_64}-w64-mingw32; but it contains changes to Ada, libgo, libgomp and libvtv, which I don't 
usually build and test.




-- 
Best regards,
LIU Hao