[master] Fix bug introduced in trac 900 change

Add MessageReader virtual destructor.  The NetBSD compiler complained
that no virtual destructor had been declared when there were virtual
methods in the class.

src/lib/log/message_reader.h

@@ -64,6 +64,9 @@ public:
         dictionary_(dictionary)
     {}
 
+    /// \brief Virtual Destructor
+    virtual ~MessageReader()
+    {}
 
     /// \brief Get Dictionary
     ///