[glibmm] Gio::ActionMap::add_action_vfunc(): Const correction.

[Murray Cumming <murrayc src gnome org>]

commit 44839efa1b5a4b54bb42b26d99cdef0978d9ac6d
Author: Murray Cumming <murrayc murrayc com>
Date:   Fri Dec 2 13:01:08 2016 +0100

    Gio::ActionMap::add_action_vfunc(): Const correction.
    
    We can do this now that we can break ABI.

 gio/src/actionmap.hg |    7 +++----
 1 files changed, 3 insertions(+), 4 deletions(-)
---
diff --git a/gio/src/actionmap.hg b/gio/src/actionmap.hg
index 518c089..b5f885d 100644
--- a/gio/src/actionmap.hg
+++ b/gio/src/actionmap.hg
@@ -181,10 +181,9 @@ public:
 #m4 _CONVERSION(`Glib::RefPtr<Action>', `GAction*', `Glib::unwrap($3)')
   _WRAP_VFUNC(Glib::RefPtr<Action> lookup_action(const Glib::ustring& name) const, "lookup_action", 
refreturn)
 
-  //TODO: Change this to use const & when we can break ABI.
-  // ( Changing it causes a symbol lookup error when trying to run already-built applications. )
-#m4 _CONVERSION(`GAction*', `Glib::RefPtr<Action>', `Glib::wrap($3, true)')
-  _WRAP_VFUNC(void add_action(Glib::RefPtr<Action> action) const, "add_action")
+#m4 _CONVERSION(`GAction*', `const Glib::RefPtr<Action>&', `Glib::wrap($3, true)')
+  _WRAP_VFUNC(void add_action(const Glib::RefPtr<Action>& action) const, "add_action")
+
   _WRAP_VFUNC(void remove_action(const Glib::ustring& name), "remove_action")
 };