always output proof state: there is only one output buffer in Isabelle/VSCode;

--- a/src/Tools/VSCode/src/server.scala	Wed Mar 15 20:39:23 2017 +0100
+++ b/src/Tools/VSCode/src/server.scala	Wed Mar 15 21:52:04 2017 +0100
@@ -233,7 +233,8 @@
                 delay_load.invoke()
           }
 
-        Some(new Session(options, resources))
+        val session_options = options.bool("editor_output_state") = true
+        Some(new Session(session_options, resources))
       }
       catch { case ERROR(msg) => reply(msg); None }