[gtkmm/gtkmm-3-24] treeiter.hg: Declare TreeValueProxy copy constructor =default

[Kjell Ahlstedt <kjellahl src gnome org>]

commit f440159623a9c06cc81478b55f5f42ea2723597c
Author: Kjell Ahlstedt <kjellahlstedt gmail com>
Date:   Tue Feb 15 15:49:50 2022 +0100

    treeiter.hg: Declare TreeValueProxy copy constructor =default
    
    Avoid warnings from the clang++ compiler.
    
    It's deprecated to implicitly declare a copy constructor, if there
    is a user-deleted (=delete) copy assignment operator.

 gtk/src/treeiter.hg | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/gtk/src/treeiter.hg b/gtk/src/treeiter.hg
index 636d8461..b5383d7e 100644
--- a/gtk/src/treeiter.hg
+++ b/gtk/src/treeiter.hg
@@ -222,6 +222,7 @@ class TreeValueProxy
 public:
 #ifndef DOXYGEN_SHOULD_SKIP_THIS
   inline TreeValueProxy(const TreeRow& row, const TreeModelColumn<ColumnType>& column);
+  TreeValueProxy(const TreeValueProxy& other) = default;
 #endif
 
   inline TreeValueProxy<ColumnType>& operator=(const ColumnType& data);