Define unambiguous Is{List,Text}Empty() in wxOwnerDrawnComboBox.

Like in wxComboBox itself, it's useful to provide these methods to avoid
problems with ambiguous IsEmpty(), inherited from both wxTextEntry and
wxItemContainer.

Closes #16618.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@78015 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/odcombo.h

@@ -315,6 +315,10 @@ public:
     virtual void Select(int n);
     virtual int GetSelection() const wxOVERRIDE;
 
+    // See wxComboBoxBase discussion of IsEmpty().
+    bool IsListEmpty() const { return wxItemContainer::IsEmpty(); }
+    bool IsTextEmpty() const { return wxTextEntry::IsEmpty(); }
+
     // Override these just to maintain consistency with virtual methods
     // between classes.
     virtual void Clear() wxOVERRIDE;