Fix compilation error on Mac

[LimingFang]

1. Replace boost pointer container with std container in AsyncLogging( std::vector<std::unique_ptr<T>> actually).
2. When CMAKE_BUILD_NO_EXAMPLES=ON, we shouldn't build cdns(I think), since it's under example directory.

[ggandycong]

刘德聪，已经收到你的邮件，请你放心 祝你生活愉快，笑口常开