Importing usr.bin/write

Replaces commands/write. No Minix-specific changes needed.

The NetBSD version lacks a few features that were present
in the Minix version: cbreak mode, verbose, and shell escapes,
but the main write(1) functionality is there and working.

Change-Id: I87b9589c54d3595d26247d221bb3d1f613feeb8c

usr.bin/write/Makefile

@@ -0,0 +1,15 @@
+#	$NetBSD: Makefile,v 1.8 2007/05/28 12:06:33 tls Exp $
+#	from: @(#)Makefile	8.1 (Berkeley) 6/6/93
+
+.include <bsd.own.mk>
+
+USE_FORT?= yes	# setgid
+PROG=	write
+SRCS=	write.c utmpentry.c term_chk.c
+BINMODE=2555
+BINGRP=	tty
+
+.PATH.c: ${NETBSDSRCDIR}/usr.bin/who
+CPPFLAGS+=-I${NETBSDSRCDIR}/usr.bin/who -DSUPPORT_UTMPX -DSUPPORT_UTMP
+
+.include <bsd.prog.mk>