Add wxCheckListBox::GetCheckedItems() helper.

This method is similar to wxListBox::GetSelections() and allows to retrieve
all checked items at once.

Closes #14969.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73422 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

interface/wx/checklst.h

@@ -151,6 +151,19 @@ public:
             Index of item whose check status is to be returned.
     */
     bool IsChecked(unsigned int item) const;
-    
+
+    /**
+        Return the indices of the checked items.
+
+        @param checkedItems
+            A reference to the array that is filled with the indices of the
+            checked items.
+        @return The number of checked items.
+
+        @see Check(), IsChecked()
+
+        @since 2.9.5
+    */
+    unsigned int GetCheckedItems(wxArrayInt& checkedItems) const;
 };