dup2 simulator

[gwyn%brl-vld at sri-unix.UUCP]

From:      Doug Gwyn (VLD/VMB) <gwyn at brl-vld>

Your dup(2) emulation incorrectly returns an error indication if
fildes2 is not open.  The close(fildes2) return value should not
be tested:
	(void)close(fildes2);