tree.cc (_Rb_tree_increment, [...]): Mark nothrow; update uses of _Rb_tree_rotate_left, _Rb_tree_rotate_right.

	* tree.cc (_Rb_tree_increment, _Rb_tree_decrement,
	_Rb_tree_rebalance_for_erase, _Rb_tree_black_count): Mark nothrow;
	update uses of _Rb_tree_rotate_left, _Rb_tree_rotate_right.
	(_Rb_tree_rotate_left, _Rb_tree_rotate_right): Make wrapper and break
	out body to ...
	(local_Rb_tree_rotate_left, local_Rb_tree_rotate_right): New static
	functions.
	* stl_tree.h (_Rb_tree_increment, _Rb_tree_decrement,
	_Rb_tree_insert_and_rebalance, _Rb_tree_rebalance_for_erase,
	_Rb_tree_black_count): Mark nothrow.

From-SVN: r146184