First part of Bug #243680 --> Marking mails as "not junk" does not update training.dat / spam filter does not create that file at all.

No one was ever calling shutdown on the plugin so we never forced ourselves to save the training data
if it was dirty.

sr=bienvenu

mailnews/extensions/bayesian-spam-filter/src/nsBayesianFilter.cpp

@@ -826,7 +826,12 @@ nsBayesianFilter::nsBayesianFilter()
     }
 }
 
-nsBayesianFilter::~nsBayesianFilter() {}
+nsBayesianFilter::~nsBayesianFilter() 
+{
+  // call shutdown when we are going away in case we need
+  // to flush the training set to disk
+  Shutdown();
+}
 
 // this object is used for one call to classifyMessage or classifyMessages(). 
 // So if we're classifying multiple messages, this object will be used for each message.