No documentation for \n[.O]

[Larry Jones]

The .O number register is undocumented.  Here's a diff to add it to the
groff_diff man page.  (Note that I've chose to document it as a
read-only register in accordance with its name even though it appears to
be a read/write register in the code.)

Index: man/groff_diff.man
===================================================================
RCS file: /sources/groff/groff/man/groff_diff.man,v
retrieving revision 1.73
diff -u -r1.73 groff_diff.man
--- man/groff_diff.man  31 Dec 2009 07:49:46 -0000      1.73
+++ man/groff_diff.man  1 Jun 2010 20:36:46 -0000
@@ -2790,6 +2790,11 @@
 1\~if no-space mode is active, 0\~otherwise.
 .
 .TP
+.B \[rs]n[.O]
+The current output level as set with
+.BR \[rs]O .
+.
+.TP
 .B \[rs]n[.pe]
 1\~during a page ejection caused by the
 .B bp
-- 
Larry Jones

ANY idiot can be famous.  I figure I'm more the LEGENDARY type! -- Calvin