Do not run some tests if no X display is available
Index: sgf2dg-4.026/t/Dg2Tk.t
===================================================================
--- sgf2dg-4.026.orig/t/Dg2Tk.t	2007-11-07 16:04:00.000000000 +0100
+++ sgf2dg-4.026/t/Dg2Tk.t	2008-01-10 07:59:36.000000000 +0100
@@ -18,6 +18,13 @@
     plan(skip_all => "Canvas not found: $@");
 }
 
+if (! exists($ENV{'DISPLAY'})) {
+    plan(skip_all => "No X display (no DISPLAY environment variable)");
+}
+
+if ($ENV{'DISPLAY'} eq '') {
+    plan(skip_all => "No X display (DISPLAY environment variable is empty)");
+}
 
 plan (tests => 6);