Made the behaviour of Thread::Wait consistent across implementations when called from its owner thread

include/SFML/System/Thread.hpp

@@ -152,6 +152,8 @@ public :
     /// thread's function ends.
     /// Warning: if the thread function never ends, the calling
     /// thread will block forever.
+    /// If this function is called from its owner thread, it
+    /// returns without doing anything.
     ///
     ////////////////////////////////////////////////////////////
     void Wait();

src/SFML/System/Win32/ThreadImpl.cpp

@@ -57,7 +57,12 @@ ThreadImpl::~ThreadImpl()
 void ThreadImpl::Wait()
 {
     if (myThread)
-        WaitForSingleObject(myThread, INFINITE);
+    {
+        // The following condition avoids a deadlock if Wait() is called from its
+        // owner thread. This makes the behaviour consistent with the Unix implementation
+        if (GetThreadId(myThread) != GetCurrentThreadId())
+            WaitForSingleObject(myThread, INFINITE);
+    }
 }