PTY: split off from TTY

Requires recreation of /dev/tty[pq]*, /dev/pty[pq]* device nodes.

Change-Id: I0e5a28d82faa934497fd3b97d619e506bcb5f439

etc/system.conf

@@ -707,3 +707,13 @@ service uds
 	;
 	uid	0;	# only for checkperms(2) and copyfd(2)
 };
+
+service pty
+{
+	system
+		KILL		# 06
+	;
+	ipc
+		SYSTEM vfs rs vm
+	;
+};

etc/usr/rc

@@ -196,6 +196,8 @@ start|autoboot)
 	up inet -script /etc/rs.inet -dev /dev/ip
     fi
 
+    up pty -dev /dev/ptyp0
+
     up uds -dev /dev/uds
 
     up -n ipc