tuned window size for the sake of Windows L&F;

--- a/src/Pure/GUI/system_dialog.scala	Sat Jan 17 23:12:02 2015 +0100
+++ b/src/Pure/GUI/system_dialog.scala	Sat Jan 17 23:33:21 2015 +0100
@@ -79,8 +79,8 @@
 
     val text = new TextArea {
       editable = false
-      columns = 50
-      rows = 20
+      columns = 65
+      rows = 24
     }
 
     val scroll_text = new ScrollPane(text)