tty: use proper i-f-serial

...the one starting agetty in installer if told so (0.4+);
also improve runlevel 2 with potential serial access.

features.in/tty/config.mk

@@ -3,6 +3,7 @@ use/tty:
 	@$(call xport,TTY_DEV)
 	@$(call xport,TTY_RATE)
 ifeq (distro,$(IMAGE_CLASS))
+	@$(call add,INSTALL2_PACKAGES,installer-feature-serial-stage2)
 	@$(call add,BASE_PACKAGES,installer-feature-serial-stage3)
 endif
 

features.in/tty/rootfs/image-scripts.d/50-serial

@@ -12,7 +12,7 @@ if ! grep -q "$BIN" "$CFG"; then
 	n=0
 	for t in $GLOBAL_TTY_DEV; do
 		grep -q "$t" "$SEC" || echo "$t" >>"$SEC"
-		echo "T$n:345:respawn:$BIN -L $t $GLOBAL_TTY_RATE vt100" >> $CFG
+		echo "T$n:2345:respawn:$BIN -L $t $GLOBAL_TTY_RATE vt100" >>$CFG
 		n=$(($n+1))
 	done
 fi