Add wxUSE_THREADS checks around wxMSW functions dealing with threads.

This removes the code unneeded in wxUSE_THREADS==0 build and also fixes
compilation of wxGUIAppTraits::WaitForThread() which didn't compile any more
with wxUSE_THREADS==0 since r67185.

Closes #13050.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@67288 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/msw/app.cpp

@@ -219,6 +219,7 @@ void wxGUIAppTraits::AfterChildWaitLoop(void *dataOrig)
     delete data;
 }
 
+#if wxUSE_THREADS
 bool wxGUIAppTraits::DoMessageFromThreadWait()
 {
     // we should return false only if the app should exit, i.e. only if
@@ -258,6 +259,7 @@ DWORD wxGUIAppTraits::WaitForThread(WXHANDLE hThread, int flags)
                QS_ALLPOSTMESSAGE
              );
 }
+#endif // wxUSE_THREADS
 
 wxPortId wxGUIAppTraits::GetToolkitVersion(int *majVer, int *minVer) const
 {