Move wxAdv library contents into wxCore

This basically removes the "adv" library, even though it's still
preserved for compatibility with user make/project files referring to
it.

It is done because the distinction between "adv" and "core" was never
really clear (e.g. why wxTreeCtrl was in core but wxTreeListCtrl in
adv?) and it prevented some core classes from using adv ones.

include/wx/unix/taskbarx11.h

@@ -11,9 +11,9 @@
 #ifndef _WX_UNIX_TASKBAR_H_
 #define _WX_UNIX_TASKBAR_H_
 
-class WXDLLIMPEXP_FWD_ADV wxTaskBarIconArea;
+class WXDLLIMPEXP_FWD_CORE wxTaskBarIconArea;
 
-class WXDLLIMPEXP_ADV wxTaskBarIcon: public wxTaskBarIconBase
+class WXDLLIMPEXP_CORE wxTaskBarIcon: public wxTaskBarIconBase
 {
 public:
     wxTaskBarIcon();