stl_tree.h (_Rb_tree::_M_end()): Return _Base_ptr instead of downcasting.

stl_tree.h (_Rb_tree::_M_end()): Return _Base_ptr instead of downcasting.

	* include/bits/stl_tree.h (_Rb_tree::_M_end()): Return _Base_ptr
	instead of downcasting.
	(_Rb_tree::_M_copy): Change second parameter to _Base_ptr.
	(_Rb_tree::_M_lower_bound, _Rb_tree:_M_upper_bound): Likewise.
	(_Rb_tree::_S_iter): Remove.
	(_Rb_tree::_S_lower_bound_tr, _Rb_tree::_S_upper_bound_tr): Remove.
	(_Rb_tree::_M_find_tr(const _Kt&) const): Call _M_lower_bound_tr
	instead of _S_lower_bound_tr
	(_Rb_tree::_M_find_tr(const _Kt&)): Call const overload.
	(_Rb_tree::_M_lower_bound_tr(const _Kt&) const): Do the search here
	instead of calling _S_lower_bound_tr.
	(_Rb_tree::_M_lower_bound_tr(const _Kt&)): Call const overload.
	(_Rb_tree::_M_upper_bound_tr(const _Kt&) const): Do the search here
	instead of calling _S_upper_bound_tr.
	(_Rb_tree::_M_upper_bound_tr(const _Kt&)): Call const overload.
	(_Rb_tree::_M_equal_range_tr(const _Kt&)): Likewise.
	(_Rb_tree::equal_range): Use _Base_ptr for end pointer.
	(_Rb_tree::_M_get_insert_unique_pos): Likewise.
	(_Rb_tree::_M_get_insert_equal_pos): Likewise.
	(_Rb_tree::_M_insert_equal_lower_node): Likewise.
	(_Rb_tree::_M_insert_unique, _Rb_tree::_M_emplace_unique,
	_Rb_tree::_M_emplace_hint_unique): Remove static_cast.

From-SVN: r223746