c++ version completed not tested yet.
	modified:   ch02/2.6/cpp_src/lexer/lexer.cpp
	modified:   ch02/2.6/cpp_src/lexer/main.cpp
	modified:   ch02/2.6/cpp_src/lexer/token.h
cpp version finished.
	modified:   ch02/2.6/cpp_src/lexer/main.cpp