More editing. Use gcc, not ld to link. On native Win32 use _unlink(). Use

More editing. Use gcc, not ld to link. On native Win32 use _unlink(). Use

	* README.win32: More editing.
	* build-dll: Use gcc, not ld to link.
	* glib.h: On native Win32 use _unlink().
	* gscanner.c: Use corrent NATIVE_WIN32 feature test macro,
	not _MSC_VER.
	* gstring.c: Include <io.h> on Win32 for _read prototype.
	* gutils.c: Remove old IO channel code (was in #if 0).
	* makefile.cygwin: Don't need to link with kernel32 and msvcrt
	explicitly, they are included anyway.