HIG: the label should specify what it's a label for

Change-Id: I196812200ab82ba0d457b59022f472f942615220
(cherry picked from commit 0196c1c9)

vcl/unx/gtk/fpicker/SalGtkFilePicker.cxx

@@ -207,6 +207,7 @@ SalGtkFilePicker::SalGtkFilePicker( const uno::Reference< uno::XComponentContext
         gtk_container_add( GTK_CONTAINER( m_pAligns[i]), m_pLists[i] );
         gtk_box_pack_end( GTK_BOX( m_pHBoxs[i] ), m_pAligns[i], false, false, 0 );
         gtk_box_pack_end( GTK_BOX( m_pHBoxs[i] ), m_pListLabels[i], false, false, 0 );
+        gtk_label_set_mnemonic_widget( GTK_LABEL(m_pListLabels[i]), m_pLists[i] );
         gtk_box_set_spacing( GTK_BOX( m_pHBoxs[i] ), 12 );
 
         gtk_box_pack_end( GTK_BOX( m_pVBox ), m_pHBoxs[i], false, false, 0 );