This threes example is for the MinGW32 compiler (a Windows
implementation of the GNU C/C++ compiler).

Note:
- The Ox development header files must be found during
  compilation. If necessary, modify Makefile.
- Compilation will do nothing, because the DLL is already
  up to date. Delete threes.o and threes.dll to check
  compilation.
- If compilation is successful, threes.dll will be created.
- oxl threes.ox to check the compiled DLL.
- ox/dev/liboxwin.a is the import library for the Ox DLL,
  created with:
  		dlltool -d oxwin_mingw.def --dllname oxwin.dll
				--output-lib liboxwin.a --export-all --kill-at
  NB1: in MINGW32 stdcall functions have no _ prefix but do use the
	   @nn suffix.
  NB2: jdsystem.h defines __stdcall (used for JDCALL and OXCALL) and
       __cdecl.
- Ox expects the Visual C++ naming conventien (_ prefix and @## suffix),
which is why threes.def contains:
        FnThrees = FnThrees@12
