[glibmm/sigc3v2] Binding: TransformProp: Don't remove from functor_base.

[Murray Cumming <murrayc src gnome org>]

commit 9f6d41e4d51314ea30f077125d451d66f441c3b6
Author: Murray Cumming <murrayc murrayc com>
Date:   Thu Apr 14 11:03:21 2016 +0200

    Binding: TransformProp: Don't remove from functor_base.
    
    Because it has been removed from the libsigc++-3.0 APi,
    because it is no longer useful.

 configure.ac        |    2 +-
 glib/src/binding.hg |    3 +--
 2 files changed, 2 insertions(+), 3 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index ba3281f..a667b78 100644
--- a/configure.ac
+++ b/configure.ac
@@ -64,7 +64,7 @@ AS_IF([test "x$enable_static" = xyes],
 
 glibreq='2.0 >= 2.48.0'
 
-GLIBMM_MODULES="sigc++-3.0 >= 2.9.1 glib-$glibreq gobject-$glibreq gmodule-$glibreq"
+GLIBMM_MODULES="sigc++-3.0 >= 2.99.5 glib-$glibreq gobject-$glibreq gmodule-$glibreq"
 GIOMM_MODULES="$GLIBMM_MODULES gio-$glibreq"
 test "x$glibmm_host_windows" = xyes || GIOMM_MODULES="$GIOMM_MODULES gio-unix-$glibreq"
 
diff --git a/glib/src/binding.hg b/glib/src/binding.hg
index cb53709..730baad 100644
--- a/glib/src/binding.hg
+++ b/glib/src/binding.hg
@@ -391,10 +391,9 @@ private:
   // The functor TransformProp can be implicitly converted to a SlotTransform
   // and used in a call to bind_property_value().
   template <typename T_from, typename T_to>
-  class TransformProp : public sigc::functor_base
+  class TransformProp
   {
   public:
-    using result_type = bool;
     using SlotTypedTransform = sigc::slot<bool(const T_from&, T_to&)>;
 
     TransformProp(const SlotTypedTransform& slot) : typed_transform(slot) {}