get number of cpu, using multiple concurrent job processes;
issue #2789: Adds Map, Dictionary perf test, not yet finished.
Removes unused cast in CCTMXTiledMap.cpp.
issue #2789: Improves performance for Map<K,V>::keys.
issue #2789: Adds performance test for Map<K, V> and Dictionary.
closed #2789: Adds a macro ‘’USE_STD_UNORDERED_MAP” for switching the implementation of Map<K, V> between using std::unordered_map and std::map.
Update CHANGELOG [ci skip]
A typo fix in EventDispatcher, DirtyFlag::FIXED_PRITORY —> DirtyFlag::FIXED_PRIORITY.