Fix wxBannerWindowNameStr definition in DLL builds.

Don't use WXDLLEXPORT_DATA when defining the variable, it can be only used
when declaring it.

This fixes wxMSW DLL build with MSVC.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@68860 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/generic/bannerwindow.cpp

@@ -35,7 +35,7 @@ const int MARGIN_Y = 5;
 
 } // anonymous namespace
 
-extern WXDLLEXPORT_DATA(const char) wxBannerWindowNameStr[] = "bannerwindow";
+const char wxBannerWindowNameStr[] = "bannerwindow";
 
 BEGIN_EVENT_TABLE(wxBannerWindow, wxWindow)
     EVT_SIZE(wxBannerWindow::OnSize)