[support8785] Verbose Exception::what() has been implemented.

This change by itself does nothing, but it allows changing
  e.what() to e.what(true) to get more details about an exception.
  This can be useful for exception debugging.

src/lib/exceptions/exceptions.h

@@ -73,6 +73,16 @@ public:
     ///
     /// @return A C-style character string of the exception cause.
     virtual const char* what() const throw();
+
+    /// \brief Returns a C-style charater string of the cause of exception.
+    ///
+    /// With verbose set to true, also returns file name and line numbers.
+    /// Note that we can't simply define a single what() method with parameters,
+    /// as the compiler would complain that it shadows the base class method.
+    ///
+    /// \param verbose if set to true, filename and line number will be added.
+    /// \return A C-style character string of the exception cause.
+    virtual const char* what(bool verbose) const throw();
     //@}
 
     ///