added successor
 On branch ch12
	modified:   ch12/binary_search_tree.hpp
add successor()
 On branch ch12
	modified:   ch12/binary_search_tree.hpp
renamed next to up
 On branch ch12
	modified:   ch12/binary_search_tree.hpp
add and test predecessor
 On branch ch12
	modified:   ch12/binary_search_tree.hpp
	modified:   ch12/main.cpp