init: changed to mount rootfs as read-only by default, just like the kernel itself does

http://lxr.linux.no/linux+v2.6.27.18/init/do_mounts.c#L25

initramfs/etc_rc.d_rc.sysinit.sh

@@ -45,7 +45,7 @@ done
 cat > /etc/conf/idunn <<EOT
 rootfs="/rootfs"
 root="$root"
-root_mode="${root_mode:-rw}"
+root_mode="${root_mode:-ro}"
 init="${init:-/sbin/init}"
 initopt="$*"
 EOT