[gtkmm] demos: Remove the ButtonBox demo

[Kjell Ahlstedt <kjellahl src gnome org>]

commit 6536a925445e1058e15b68de47bf2d15b4d314b8
Author: Kjell Ahlstedt <kjellahlstedt gmail com>
Date:   Thu Feb 7 10:52:35 2019 +0100

    demos: Remove the ButtonBox demo

 demos/Makefile.am                   |   1 -
 demos/gtk-demo/demo.gresource.xml   |   1 -
 demos/gtk-demo/demos.h              |   3 -
 demos/gtk-demo/example_buttonbox.cc | 106 ------------------------------------
 4 files changed, 111 deletions(-)
---
diff --git a/demos/Makefile.am b/demos/Makefile.am
index 6fbc1a39..a25e8da7 100644
--- a/demos/Makefile.am
+++ b/demos/Makefile.am
@@ -38,7 +38,6 @@ dist_noinst_DATA = \
 GTK_DEMOS = \
   gtk-demo/example_appwindow.cc \
   gtk-demo/example_builder.cc \
-  gtk-demo/example_buttonbox.cc \
   gtk-demo/example_change_display.cc \
   gtk-demo/example_colorsel.cc \
   gtk-demo/example_dialog.cc \
diff --git a/demos/gtk-demo/demo.gresource.xml b/demos/gtk-demo/demo.gresource.xml
index 8d430986..f66cb847 100644
--- a/demos/gtk-demo/demo.gresource.xml
+++ b/demos/gtk-demo/demo.gresource.xml
@@ -37,7 +37,6 @@
   <gresource prefix="/sources">
     <file>example_appwindow.cc</file>
     <file>example_builder.cc</file>
-    <file>example_buttonbox.cc</file>
     <file>example_change_display.cc</file>
     <file>example_colorsel.cc</file>
     <file>example_dialog.cc</file>
diff --git a/demos/gtk-demo/demos.h b/demos/gtk-demo/demos.h
index f18c879d..794460f1 100644
--- a/demos/gtk-demo/demos.h
+++ b/demos/gtk-demo/demos.h
@@ -13,10 +13,8 @@ struct Demo
   Demo* children;
 };
 
-
 Gtk::Window* do_appwindow();
 Gtk::Window* do_builder();
-Gtk::Window* do_buttonbox();
 Gtk::Window* do_change_display();
 Gtk::Window* do_colorsel();
 Gtk::Window* do_dialog();
@@ -54,7 +52,6 @@ Demo testgtk_demos[] =
 {
   { "Application main window", "example_appwindow.cc", sigc::ptr_fun(&do_appwindow), nullptr },
   { "Builder", "example_builder.cc", sigc::ptr_fun(&do_builder), nullptr },
-  { "Button Boxes", "example_buttonbox.cc",  sigc::ptr_fun(&do_buttonbox), nullptr },
   { "Change Display", "example_change_display.cc", sigc::ptr_fun(&do_change_display), nullptr },
   { "Color Chooser", "example_colorsel.cc", sigc::ptr_fun(&do_colorsel), nullptr },
   { "Dialog and Message Boxes", "example_dialog.cc", sigc::ptr_fun(&do_dialog), nullptr },