Turn off timestamping after the warning.

src/ChangeLog

@@ -1,6 +1,7 @@
 2008-05-12  Micah Cowan  <micah@cowan.name>
 
-	* main.c (main): Downgrade "-N with -O" to a warning.
+	* main.c (main): Downgrade "-N with -O" to a warning, and switch
+	it off to avoid confusing messages.
 
 2008-04-30  Micah Cowan  <micah@cowan.name>
 

src/main.c

@@ -903,6 +903,7 @@ will be placed in the single file you specified.\n\n"));
           logprintf (LOG_NOTQUIET, "%s", _("\
 WARNING: timestamping does nothing in combination with -O. See the manual\n\
 for details.\n\n"));
+          opt.timestamping = false;
         }
     }