Commit Derek Price's patch to eliminate obsolete ndir.h, with some
	trivial fine-tuning:

	* windows-NT/ndir.c, ndir.h: Move to...
	* windows-NT/dirent.c, dirent.h: ...here, and modify to meet POSIX
	dirent.h API
	* windows-NT/Makefile.am (EXTRA_DIST): Rename ndir.(c,h) to dirent.(c,h)
	* windows-NT/config.h.in.in [HAVE_SYS_DIR_H, HAVE_SYS_NDIR_H]: Remove
	obsolete macros.
	[HAVE_DIRENT_H]: Define