small doc fix

[Clint Adams]

I think this better describes -v's behavior.

Index: bogofilter.xml
===================================================================
RCS file: /cvsroot/bogofilter/bogofilter/bogofilter.xml,v
retrieving revision 1.9
diff -u -r1.9 bogofilter.xml
--- bogofilter.xml	29 Sep 2002 21:43:47 -0000	1.9
+++ bogofilter.xml	3 Oct 2002 03:59:53 -0000
@@ -108,8 +108,10 @@
 
 <para>The <option>-v</option> option produces a report to standard 
 output on <application>bogofilter</application>'s analysis af the
-input. The report lists the tokens with highest deviation from a mean
-of 0.5 association with spam.</para>
+input. Each additional <option>v</option> will increase the verbosity of
+the output, up to a maximum of 4.  With <option>-vv</option>, the report
+lists the tokens with highest deviation from a mean of 0.5 association
+with spam.</para>
 
 <para>The <option>-V</option> option prints the version number and 
 exits.</para>