Replace the /dev/stdin, /dev/stdout, and /dev/stderr nodes with

symlinks to fd/0, fd/1, and fd/2 respectively.  This will make
things easier for upcoming changes to fdesc (and does not break
anything for the current state of things) and hopefully its
position as the replacement for our existing static /dev/fd nodes.

Suggested (and reviewed) by:	phk

etc/MAKEDEV

@@ -307,9 +307,6 @@ std)
 	mknod io	c 2 14;			chmod 600 io
 	mknod tty	c 1 0;			chmod 666 tty
 	mknod klog	c 7 0;			chmod 600 klog
-	mknod stdin	c 22 0; 		chmod 666 stdin
-	mknod stdout	c 22 1; 		chmod 666 stdout
-	mknod stderr	c 22 2; 		chmod 666 stderr
 	mknod pci	c 78 0; 		chmod 644 pci
 	mkdir -p fd
 	(cd fd && i=0 &&
@@ -320,6 +317,9 @@ std)
 	)
 	chmod 555 fd
 	chmod 666 fd/*
+	ln -sf fd/0 stdin
+	ln -sf fd/1 stdout
+	ln -sf fd/2 stderr
 	;;
 
 jail)