[libsigc++2] Add an include in limit_reference.h

[Kjell Ahlstedt <kjellahl src gnome org>]

commit df361299c3f9a0922a683e5fa3869764932bb19a
Author: Kjell Ahlstedt <kjell ahlstedt bredband net>
Date:   Fri Aug 8 12:47:02 2014 +0200

    Add an include in limit_reference.h
    
    * sigc++/macros/limit_reference.h.m4: limit_reference.h must include
    visit_each.h, with the primary definition of template struct visitor.
    https://mail.gnome.org/archives/libsigc-list/2014-August/msg00001.html

 sigc++/macros/limit_reference.h.m4 |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/sigc++/macros/limit_reference.h.m4 b/sigc++/macros/limit_reference.h.m4
index 802446c..bb4b3b7 100644
--- a/sigc++/macros/limit_reference.h.m4
+++ b/sigc++/macros/limit_reference.h.m4
@@ -137,6 +137,7 @@ divert(0)
 
 _FIREWALL([LIMIT_REFERENCE])
 
+#include <sigc++/visit_each.h>
 #include <sigc++/type_traits.h>
 #include <sigc++/trackable.h>