Summary:
- From http://hg.openjdk.java.net/mlvm/mlvm/hotspot/file/4cd7d914b0e3/coro-simple.patch.
- Resolve trivial conflicts in: systemDictionary.hpp, thread.cpp, debug.hpp.
- Add an option "EnableCoroutine".

Test Plan: run jtreg tests

Reviewed-by: yuleil, shiyuexw, sanhong

Issue: https://github.com/alibaba/dragonwell8/issues/113