[gtkmm] HeaderBar demo: Use the pan-start-symbolic and pan-end-symbolic icons

[Kjell Ahlstedt <kjellahl src gnome org>]

commit 1d0732322711dbfa495f0bba99d8ac7024c8d3c9
Author: Kjell Ahlstedt <kjell ahlstedt bredband net>
Date:   Sun May 22 15:43:24 2016 +0200

    HeaderBar demo: Use the pan-start-symbolic and pan-end-symbolic icons
    
    These icons have been around for about two years now. They should be
    available in most systems.

 demos/gtk-demo/example_headerbar.cc |    6 ------
 1 files changed, 0 insertions(+), 6 deletions(-)
---
diff --git a/demos/gtk-demo/example_headerbar.cc b/demos/gtk-demo/example_headerbar.cc
index 173b0ba..44022dc 100644
--- a/demos/gtk-demo/example_headerbar.cc
+++ b/demos/gtk-demo/example_headerbar.cc
@@ -15,7 +15,6 @@
 // See https://bugzilla.gnome.org/show_bug.cgi?id=729565
 // If they are not available in your selected icon theme, perhaps you can
 // use the go-[up,down,previous,next]-symbolic icons.
-#define USE_PAN_ICON_NAMES 0
 
 class Example_HeaderBar : public Gtk::Window
 {
@@ -93,13 +92,8 @@ void Example_HeaderBar::configure_arrow_buttons()
 {
   m_arrow_buttons_box.get_style_context()->add_class("linked");
 
-#if USE_PAN_ICON_NAMES
   m_left_arrow_button.set_image_from_icon_name("pan-start-symbolic", Gtk::ICON_SIZE_BUTTON, true);
   m_right_arrow_button.set_image_from_icon_name("pan-end-symbolic", Gtk::ICON_SIZE_BUTTON, true);
-#else
-  m_left_arrow_button.set_image_from_icon_name("go-previous-symbolic", Gtk::ICON_SIZE_BUTTON, true);
-  m_right_arrow_button.set_image_from_icon_name("go-next-symbolic", Gtk::ICON_SIZE_BUTTON, true);
-#endif
 
   m_arrow_buttons_box.add(m_left_arrow_button);
   m_arrow_buttons_box.add(m_right_arrow_button);