[C++ PATCH] Rewrite convert_nontype_argument

[Gabriel Dos Reis]

Giovanni Bajo:

> + #define TYPE_REFOB_P(NODE)    \
> +   (TREE_CODE (NODE) == REFERENCE_TYPE   \
> +    && TREE_CODE (TREE_TYPE (NODE)) != FUNCTION_TYPE \
> +    && TREE_CODE (TREE_TYPE (NODE)) != METHOD_TYPE \
> +    && TREE_CODE (TREE_TYPE (NODE)) != VOID_TYPE)

This is missing comment.

-- Gaby