Clean up copy-initialization in overloading code.

Clean up copy-initialization in overloading code.

        * call.c (build_user_type_conversion_1): Die if we are asked to
        convert to the same or a base type.
        (implicit_conversion): Avoid doing so.  Lose reference binding code.
        (convert_like_real): Treat BASE_CONV and RVALUE_CONV as implicit
        direct-initialization.  Also do direct-init part of copy-init.
        (build_user_type_conversion): Don't provide context to convert_like.
        * cvt.c (ocp_convert): build_user_type_conversion will now provide
        the constructor call for copy-init.

From-SVN: r38159