Minor doc change

src/exif.hpp

@@ -21,7 +21,7 @@
 /*!
   @file    exif.hpp
   @brief   Encoding and decoding of Exif data
-  @version $Name:  $ $Revision: 1.44 $
+  @version $Name:  $ $Revision: 1.45 $
   @author  Andreas Huggel (ahu)
            <a href="mailto:ahuggel@gmx.net">ahuggel@gmx.net</a>
   @date    09-Jan-04, ahu: created
@@ -505,7 +505,7 @@ namespace Exiv2 {
         //@{
         //! Copying not allowed (Todo: implement me!)
         ExifData(const ExifData& rhs);
-        //! Assignment not allowed (Todo: implement me!)
+        //! Assignment not allowed (IFD does not have an assignment operator)
         ExifData& operator=(const ExifData& rhs);
         //@}
     public: