add matrix chain
	new file:   ch15/matrix_chain.hpp
move definition for result inside
 On branch ch15
	modified:   ch15/matrix_chain.hpp
working on matrix chain
 On branch ch15
	modified:   ch15/matrix_chain.hpp
matrix chain : m is correct now, s not.
	modified:   ch15/matrix_chain.hpp
matrix chain order done.
 On branch ch15
	modified:   ch15/matrix_chain.hpp