fix thread handle leak (these don't show up as threads anywhere, but

sysinternals handle.exe shows them)

stepmania/src/arch/Threads/Threads_Win32.cpp

@@ -55,6 +55,9 @@ int ThreadImpl_Win32::Wait()
 	DWORD ret;
 	GetExitCodeThread( ThreadHandle, &ret );
 
+	CloseHandle( ThreadHandle );
+	ThreadHandle = NULL;
+
 	return ret;
 }