csync: using std::thread;

[piedar]

• No API changes!
• Eliminates dependency on pthreads-win32.
• Takes advantage of thread and mutex from C++11.
• One downside: the c_sync library is 15 kB bigger.

todo

• Should C++ globals be static? Appears yes.
• using aliases might be premature abstraction.
• Examples still depend on pthreads-win32.
• Old binaries work on new library, but there might be pitfalls on other platforms.