[gparted] Use Gtk::Box for Dialog_Progress (!25)

[Mike Fleetwood <mfleetwo src gnome org>]

commit 07fc4aefc3adcdbc93a3f9fb5ef420a015c09539
Author: Luca Bacci <luca bacci982 gmail com>
Date:   Wed Feb 27 16:55:50 2019 +0100

    Use Gtk::Box for Dialog_Progress (!25)
    
    Gtk::HBox and Gtk::VBox were deprecated in Gtkmm 3.2.  Replace with
    plain Gtk::Box.
    
    This commit makes the change for Dialog_Progress.cc.
    
    Closes !25 - Modern Gtk3 - part 1

 src/Dialog_Progress.cc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/src/Dialog_Progress.cc b/src/Dialog_Progress.cc
index c27f1ba0..e7b69303 100644
--- a/src/Dialog_Progress.cc
+++ b/src/Dialog_Progress.cc
@@ -49,7 +49,7 @@ Dialog_Progress::Dialog_Progress(const std::vector<Device>& devices, const std::
        this->property_default_width() = 700;
 
        {
-               Gtk::VBox* vbox(manage(new Gtk::VBox()));
+               Gtk::Box *vbox(manage(new Gtk::Box(Gtk::ORIENTATION_VERTICAL)));
 
                vbox->set_border_width(10);
                this->get_vbox()->pack_start(*vbox, Gtk::PACK_EXPAND_WIDGET);