* cp-tree.h (special_function_kind): Add various kinds of
	destructors.
	(special_function_p): New function.
	* class.c (overrides): Don't let one kind of destructor override
	another.
	* decl2.c (mark_used): Use DECL_NON_THUNK_FUNCTION_P when deciding
	whether or not to instantiate a template.
	* tree.c (special_function_p): Define.

From-SVN: r33668