[libsigc++2/variadic_mem_fun2] A small const improvement.

[Murray Cumming <murrayc src gnome org>]

commit cc74fe965b5fadb8921bf509a1be64931fda5196
Author: Murray Cumming <murrayc murrayc com>
Date:   Sat Mar 5 23:20:11 2016 +0100

    A small const improvement.

 sigc++/adaptors/hide.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/sigc++/adaptors/hide.h b/sigc++/adaptors/hide.h
index 443eb9f..bae6cc9 100644
--- a/sigc++/adaptors/hide.h
+++ b/sigc++/adaptors/hide.h
@@ -85,7 +85,7 @@ struct hide_functor : public adapts<T_functor>
 
        const auto t_start = internal::tuple_start<index_ignore>(t);
        const auto t_end = internal::tuple_end<size - index_ignore - 1>(t);
-       auto t_used = std::tuple_cat(t_start, t_end); //TODO: Let this be const?
+       const auto t_used = std::tuple_cat(t_start, t_end);
 
        constexpr auto size_used = size - 1;