Don't use wxCriticalSection in wxWakeUpPipeMT if wxUSE_THREADS==0.

In fact, don't define wxWakeUpPipeMT class at all when not using threads.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74513 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/unix/private/wakeuppipe.h

@@ -65,6 +65,7 @@ private:
 
 // This class can be used from multiple threads, i.e. its WakeUp() can be
 // called concurrently.
+#if wxUSE_THREADS
 
 class wxWakeUpPipeMT : public wxWakeUpPipe
 {
@@ -92,4 +93,10 @@ private:
     wxCriticalSection m_pipeLock;
 };
 
+#else // !wxUSE_THREADS
+
+typedef wxWakeUpPipe wxWakeUpPipeMT;
+
+#endif // wxUSE_THREADS/!wxUSE_THREADS
+
 #endif // _WX_UNIX_PRIVATE_WAKEUPPIPE_H_