ttsnoop: deal with iostream.h and missing sentinels.

Replacing strstream may be possible, but requires more work and a better
understanding of the code.

cde/programs/ttsnoop/ttsnoop.C.src

@@ -766,7 +766,7 @@ main(int argc, char **argv)
 		  snoopPatIsRegistered ? "Off" : "On" );
     if (optMapOnOutput) {
 	    XtVaSetValues( dtb_ttsnoop_ttsnoop_win.ttsnoopPane,
-			   DtNmapOnOutput, optMapOnOutput, 0 );
+			   DtNmapOnOutput, optMapOnOutput, NULL );
     }
     installSignalHandler();