test cases/vala/14 target glib version and gresources/gres/test.ui

<?xml version="1.0" encoding="UTF-8"?>
<interface>
  <!-- interface-requires gtk+ 3.8 -->
  <template class="TestWidget" parent="GtkBox">
    <property name="visible">True</property>
    <property name="can_focus">False</property>
    <property name="orientation">vertical</property>
    <property name="spacing">4</property>
    <child>
      <object class="GtkEntry" id="entry">
        <property name="visible">True</property>
        <property name="can_focus">True</property>
      </object>
      <packing>
        <property name="position">0</property>
      </packing>
    </child>
  </template>
</interface>