[meld/ui-next] preferences: Use headerbar and remove internal border

[Kai Willadsen <kaiw src gnome org>]

commit 22571e574c24cf6a8fcb8aab21d4e0ec3246ca42
Author: Kai Willadsen <kai willadsen gmail com>
Date:   Sat Apr 6 07:14:02 2019 +1000

    preferences: Use headerbar and remove internal border

 meld/resources/ui/preferences.ui | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)
---
diff --git a/meld/resources/ui/preferences.ui b/meld/resources/ui/preferences.ui
index d47fa235..6abd912e 100644
--- a/meld/resources/ui/preferences.ui
+++ b/meld/resources/ui/preferences.ui
@@ -22,13 +22,21 @@
     <property name="title" translatable="yes">Preferences</property>
     <property name="resizable">False</property>
     <property name="modal">True</property>
+    <property name="destroy_with_parent">True</property>
     <property name="type_hint">dialog</property>
+    <property name="use-header-bar">1</property>
     <signal name="response" handler="on_response" swapped="no"/>
-    <child>
-      <placeholder/>
+    <child type="titlebar">
+      <object class="GtkHeaderBar" id="header_bar">
+        <property name="title" translatable="yes">Preferences</property>
+        <property name="visible">True</property>
+        <property name="can_focus">False</property>
+        <property name="show-close-button">True</property>
+       </object>
     </child>
     <child internal-child="vbox">
       <object class="GtkBox" id="dialog-vbox4">
+        <property name="border-width">0</property>
         <property name="visible">True</property>
         <property name="can_focus">False</property>
         <property name="orientation">vertical</property>