Merge branch 'adv-merge'

Move the entire contents of wxAdv library into wxCore.

In the future, wxAdv will disappear entirely, but for now keep it as an
empty placeholder to allow the existing make/project files to work.

See https://github.com/wxWidgets/wxWidgets/pull/900

include/wx/msw/taskbar.h

@@ -15,9 +15,9 @@
 #include "wx/icon.h"
 
 // private helper class:
-class WXDLLIMPEXP_FWD_ADV wxTaskBarIconWindow;
+class WXDLLIMPEXP_FWD_CORE wxTaskBarIconWindow;
 
-class WXDLLIMPEXP_ADV wxTaskBarIcon : public wxTaskBarIconBase
+class WXDLLIMPEXP_CORE wxTaskBarIcon : public wxTaskBarIconBase
 {
 public:
     wxTaskBarIcon(wxTaskBarIconType iconType = wxTBI_DEFAULT_TYPE);