[gtkmm-documentation] Printing example: Remove use of Stock items.

[Murray Cumming <murrayc src gnome org>]

commit bbfc5b2c72cfb3e11d55db431d5dae15ef821fee
Author: Murray Cumming <murrayc murrayc com>
Date:   Thu Sep 26 11:48:15 2013 +0200

    Printing example: Remove use of Stock items.
    
    Stock items are now deprecated in GTK+.
    It is annoying, but here is an explanation:
    https://mail.gnome.org/archives/gtk-devel-list/2013-July/msg00005.html

 examples/book/printing/advanced/previewdialog.cc |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/examples/book/printing/advanced/previewdialog.cc 
b/examples/book/printing/advanced/previewdialog.cc
index 09b081a..340980a 100644
--- a/examples/book/printing/advanced/previewdialog.cc
+++ b/examples/book/printing/advanced/previewdialog.cc
@@ -30,7 +30,7 @@ PreviewDialog::PreviewDialog(
   m_VBox(Gtk::ORIENTATION_VERTICAL),
   m_SpinAdjustment( Gtk::Adjustment::create(1, 100, 1) ), //Used to construct m_PageSpin
   m_PageSpin(m_SpinAdjustment, 1, 0),
-  m_CloseButton(Gtk::Stock::CLOSE),
+  m_CloseButton("_Close", true),
   m_Page(1),
   m_DpiX(0),
   m_DpiY(0)