correctly paint toolbar separators with gtk-2.8 (bnc#770013)

wide_separators = 0 would be enough because the value was not modified if the
property did not exist.

Anyway, I added also #if GTK_CHECK_VERSION(2,10,0) because it helps to avoid
the GTK warning about non-existing property 'wide-separators'.

Change-Id: If93928821d951dc15da967519cb207efdaa30cf7

vcl/unx/gtk/gdi/salnativewidgets-gtk.cxx

@@ -2865,7 +2865,10 @@ sal_Bool GtkSalGraphics::NWPaintGTKToolbar(
             }
             else if( nPart == PART_SEPARATOR_HORZ || nPart == PART_SEPARATOR_VERT )
             {
-                gint separator_height, separator_width, wide_separators;
+                const double shim = 0.2;
+
+#if GTK_CHECK_VERSION(2,10,0)
+                gint separator_height, separator_width, wide_separators = 0;
 
                 gtk_widget_style_get (gWidgetData[m_nXScreen].gSeparator,
                                       "wide-separators",  &wide_separators,
@@ -2873,8 +2876,6 @@ sal_Bool GtkSalGraphics::NWPaintGTKToolbar(
                                       "separator-height", &separator_height,
                                       NULL);
 
-                const double shim = 0.2;
-
                 if (wide_separators)
                 {
                     if (nPart == PART_SEPARATOR_VERT)
@@ -2891,6 +2892,7 @@ sal_Bool GtkSalGraphics::NWPaintGTKToolbar(
                                        w * (1 - 2*shim), separator_width);
                 }
                 else
+#endif
                 {
                     if (nPart == PART_SEPARATOR_VERT)
                         gtk_paint_vline (gWidgetData[m_nXScreen].gSeparator->style, gdkDrawable,