Replace hsMutex with std::mutex
Use C++11 threading for hsEvent, and clean up the API a bit
Simplify plDispatch mutexes a bit
Move the old IPC-based semaphore to hsGlobalSemaphore, and provide a
"normal" (inter-thread only) semaphore class.
Clean up hsReaderWriterLock
Reintroduce (and enforce use of) hsLockFor{Reading,Writing}
Merge pull request #443 from zrax/cxx11_synch

C++11 synchronization primitives