Add wxListCtrl::IsVisible()

Allow checking if the given item is (at least partially) visible on
screen.

Closes https://github.com/wxWidgets/wxWidgets/pull/1444

Closes #9949.

interface/wx/listctrl.h

@@ -1088,6 +1088,16 @@ public:
     */
     void SetImageList(wxImageList* imageList, int which);
 
+    /**
+        Check if the item is visible.
+
+        An item is considered visible if at least one pixel of it is present
+        on the screen.
+
+        @since 3.1.3
+    */
+    bool IsVisible(long item) const;
+
     /**
         Sets the data of an item.