initial working version.
First working version in C++, including `set`,`unordered_map`
Merge remote-tracking branch 'github/master' into github_master
bug fix voba::set, a.first is replaced with KEY(a)
bug fix: static variable EMPTY and DELETE are not gurantee to be initialized before Assert_Empty_not_eq_Delete
fix compliation error for g++. it does not allow definition outside belonging namespace