[gtkmm-documentation] clipboard ideal example: Make the grid expand.

[Murray Cumming <murrayc src gnome org>]

commit 1caf884b6f182ae721d701df80e71ff15fbd9c3b
Author: Murray Cumming <murrayc murrayc com>
Date:   Wed May 3 13:32:06 2017 +0200

    clipboard ideal example: Make the grid expand.
    
    To match the behaviour in the gtkmm3 version.

 examples/book/clipboard/ideal/examplewindow.cc |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/examples/book/clipboard/ideal/examplewindow.cc b/examples/book/clipboard/ideal/examplewindow.cc
index 2c1c11f..7dc67cc 100644
--- a/examples/book/clipboard/ideal/examplewindow.cc
+++ b/examples/book/clipboard/ideal/examplewindow.cc
@@ -43,7 +43,7 @@ ExampleWindow::ExampleWindow()
   m_VBox.pack_start(m_Label, Gtk::PackOptions::SHRINK);
 
   //Fill Grid:
-  m_VBox.pack_start(m_Grid);
+  m_VBox.pack_start(m_Grid, Gtk::PackOptions::EXPAND_WIDGET);
   m_Grid.set_row_homogeneous(true);
   m_Grid.set_column_homogeneous(true);
   m_Grid.attach(m_ButtonA1, 0, 0, 1, 1);