Support added for building using a GNU toolchain on Win32,

	Support added for building using a GNU toolchain on Win32,
	i.e. gcc -mno-cygwin on cygwin (a.k.a. mingw32, using egcs-1.1.2).

	* README.win32: Updated.
	* build-dll makefile.cygwin tests/makefile.cygwin: New files.
	* glib.h glib.def glibconfig.h.win32 makefile.msc: Slight updates.
	* gmain.c: No need to include <fcntl.h> and <io.h> on Win32.
	* gmain.c gutils.c testglib.c tests/string-test.c: Test for
	NATIVE_WIN32, not _MSC_VER.
	* gmutex.c: Must declare g_thread_functions_for_glib_use as
	exported (using the GUTILS_C_VAR macro).
	* gutils.c gmodule/libgplugin_[ab].c: LibMain not needed.
	* gmodule/gmoduleconf.h.win32: Need underscore with gcc.
	* gthread/gthread.c: With gcc on Win32, must use memcpy to assign
	value of g_thread_functions_for_glib_use (?).
	* makefile.msc tests/makefile.msc: Cosmetics.