Fix C++11 Windows build of threading code

The initial problem was that mutex_auto_lock.h tries to use std::unique_lock<std::mutex>
	despite mutex.h not using C++11's std::mutex on Windows. The problem here is the mismatch
	between C++11 usage conditions of the two headers. This commit moves the decision logic
	to threads.h and makes sure mutex.h, mutex_auto_lock.h and event.h all use the same features.

src/threading/thread.cpp

@@ -198,7 +198,7 @@ bool Thread::kill()
 
 	m_running = false;
 
-#ifdef _WIN32
+#if USE_WIN_THREADS
 	TerminateThread(m_thread_handle, 0);
 	CloseHandle(m_thread_handle);
 #else
@@ -310,10 +310,16 @@ void Thread::setName(const std::string &name)
 
 unsigned int Thread::getNumberOfProcessors()
 {
-#if __cplusplus >= 201103L
+#if USE_CPP11_THREADS
 
 	return std::thread::hardware_concurrency();
 
+#elif USE_WIN_THREADS
+
+	SYSTEM_INFO sysinfo;
+	GetSystemInfo(&sysinfo);
+	return sysinfo.dwNumberOfProcessors;
+
 #elif defined(_SC_NPROCESSORS_ONLN)
 
 	return sysconf(_SC_NPROCESSORS_ONLN);
@@ -335,12 +341,6 @@ unsigned int Thread::getNumberOfProcessors()
 
 	return get_nprocs();
 
-#elif defined(_WIN32)
-
-	SYSTEM_INFO sysinfo;
-	GetSystemInfo(&sysinfo);
-	return sysinfo.dwNumberOfProcessors;
-
 #elif defined(PTW32_VERSION) || defined(__hpux)
 
 	return pthread_num_processors_np();
@@ -359,7 +359,7 @@ bool Thread::bindToProcessor(unsigned int proc_number)
 
 	return false;
 
-#elif defined(_WIN32)
+#elif USE_WIN_THREADS
 
 	return SetThreadAffinityMask(getThreadHandle(), 1 << proc_number);
 
@@ -407,7 +407,7 @@ bool Thread::bindToProcessor(unsigned int proc_number)
 
 bool Thread::setPriority(int prio)
 {
-#if defined(_WIN32)
+#if USE_WIN_THREADS
 
 	return SetThreadPriority(getThreadHandle(), prio);