Added comment to String constructor.

   //! Constructor from const char*

   String( const char* str );   

   //! Constructor with char pointer

   /*! @param prefix_cut_off says length of the prefix that is going to be omitted and

       @param sufix_cut_off says the same about sufix.

    */

   //////

   /// Constructor with char pointer

   ///

   /// @param prefix_cut_off says length of the prefix that is going to be omitted and

   /// @param sufix_cut_off says the same about sufix.

   String( const char* c,

           int prefix_cut_off,

           int sufix_cut_off = 0 );