document -o flag -- read only

Reference: /n/atom/patch/applied/vbladeroman
Date: Thu Jun 12 21:00:26 CES 2014
Signed-off-by: quanstro@quanstro.net

--- /sys/man/8/vblade	Thu Jun 12 21:00:19 2014
+++ /sys/man/8/vblade	Thu Jun 12 21:00:19 2014
@@ -4,7 +4,7 @@
 .SH SYNOPSIS
 .B vblade
 [
-.B -ir
+.B -iro
 ] [
 .B -s
 .I size
@@ -44,12 +44,15 @@
 All previous configuration information is lost.  Without this option,
 configuration is read from
 .I file
-and command line options override previous settings.
+and command like options override previous settings.
 .TP
 .B -r
 Raw.  Do not use a configuration header.  This is useful when
 exporting a device or file not generally exported by
 .IR vblade .
+.TP
+.B -o
+Read only.  Do now allow writes to the backing store.
 .TP
 .BI -s " n"
 The exported target will have size