Fix wxGTK 1 build after gtk/gtk.h wrapper header addition

Changes of c0b0562533 to common code broke
wxGTK1 build, as wx/gtk/private/wrapgtk.h is for wxGTK 2+ only.

Fix this by handling wxGTK 1 separately and including gtk/gtk.h directly
for it.

Hopefully this code will be removed, together with the rest of wxGTK1
support, in some not so distant future.

src/unix/taskbarx11.cpp

@@ -64,7 +64,11 @@
 // ----------------------------------------------------------------------------
 
 #if defined(__WXGTK__)
-    #include "wx/gtk/private/wrapgtk.h"
+    #ifdef __WXGTK20__
+        #include "wx/gtk/private/wrapgtk.h"
+    #else // GTK+ 1.x
+        #include <gtk/gtk.h>
+    #endif
     #include <gdk/gdkx.h>
     #define GetDisplay()        GDK_DISPLAY()
     #define GetXWindow(wxwin)   GDK_WINDOW_XWINDOW((wxwin)->m_widget->window)