[gtk+] headerbar: remove G_PARAM_CONSTRUCT from custom-title

[Christian Hergert <chergert src gnome org>]

commit 5f0a8cf136862d960c6d4985077e0176efa2c738
Author: Christian Hergert <chergert redhat com>
Date:   Tue Nov 3 14:36:54 2015 -0800

    headerbar: remove G_PARAM_CONSTRUCT from custom-title
    
    This fixes the ability to sublcass GtkHeaderBar from a UI template which
    contains a custom <child type="title"> element.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=757544

 gtk/gtkheaderbar.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/gtk/gtkheaderbar.c b/gtk/gtkheaderbar.c
index 53bd4d5..a1f0606 100644
--- a/gtk/gtkheaderbar.c
+++ b/gtk/gtkheaderbar.c
@@ -1892,7 +1892,7 @@ gtk_header_bar_class_init (GtkHeaderBarClass *class)
                            P_("Custom Title"),
                            P_("Custom title widget to display"),
                            GTK_TYPE_WIDGET,
-                           G_PARAM_READWRITE|G_PARAM_CONSTRUCT|G_PARAM_STATIC_STRINGS);
+                           G_PARAM_READWRITE|G_PARAM_STATIC_STRINGS);
 
   header_bar_props[PROP_SPACING] =
       g_param_spec_int ("spacing",