This refactor the StandAlone and WorkList files in order to use more

C++11 features remove the dependencies from OS specific code. Changes:

- Making WorkList class to have its own mutex instead of the OS specific
global one. The new mutex is the one from std library. The OS specific
code is also removed.

- Using the C++11 std library to handle threads in StandAlone
application
and enabling concurrent processing on non-windows platforms.

- converting the global variable Worklist into local variable workList.

glslang/OSDependent/Unix/ossource.cpp

@@ -184,20 +184,6 @@ void ReleaseGlobalLock()
   pthread_mutex_unlock(&gMutex);
 }
 
-// TODO: non-windows: if we need these on linux, flesh them out
-void* OS_CreateThread(TThreadEntrypoint /*entry*/)
-{
-    return 0;
-}
-
-void OS_WaitForAllThreads(void* /*threads*/, int /*numThreads*/)
-{
-}
-
-void OS_Sleep(int /*milliseconds*/)
-{
-}
-
 void OS_DumpMemoryCounters()
 {
 }