[gtkmm] Gtk::GLArea: Fix refcount in signal_create_context()

[Kjell Ahlstedt <kjellahl src gnome org>]

commit d1ae01f3dc14dfbadb3e6288c6bdab5f4a1332b5
Author: Kjell Ahlstedt <kjell ahlstedt bredband net>
Date:   Sun Apr 24 12:33:17 2016 +0200

    Gtk::GLArea: Fix refcount in signal_create_context()
    
    gtk/src/glarea.hg: wrap() must take a reference on the GdkGLContext object
    in signal_create_context().
    
    Noticed by Bill McGrory <wdmcgrory gmail com> in
    https://mail.gnome.org/archives/gtkmm-list/2016-April/msg00022.html

 gtk/src/glarea.hg |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/gtk/src/glarea.hg b/gtk/src/glarea.hg
index 686bba9..256e51c 100644
--- a/gtk/src/glarea.hg
+++ b/gtk/src/glarea.hg
@@ -97,6 +97,7 @@ public:
   _WRAP_PROPERTY("has-stencil-buffer", bool, newin "3,18")
 
 #m4 _CONVERSION(`Glib::RefPtr<Gdk::GLContext>', `GdkGLContext*', Glib::unwrap($3))
+#m4 _CONVERSION(`GdkGLContext*', `Glib::RefPtr<Gdk::GLContext>', Glib::wrap($3, true))
   _WRAP_SIGNAL(Glib::RefPtr<Gdk::GLContext> create_context(), "create_context", newin "3,18")
 #m4 _CONVERSION(`GdkGLContext*', `const Glib::RefPtr<Gdk::GLContext>&', Glib::wrap($3, true))
   _WRAP_SIGNAL(bool render(const Glib::RefPtr<Gdk::GLContext>& context), render, newin "3,18")