avoid hardwired options: use isabelle.args settings instead;

--- a/src/Tools/VSCode/extension/src/extension.ts	Mon Jan 02 17:35:51 2017 +0100
+++ b/src/Tools/VSCode/extension/src/extension.ts	Mon Jan 02 17:41:00 2017 +0100
@@ -29,13 +29,7 @@
         { command: isabelle_tool,
           args: ["vscode_server"].concat(isabelle_args) };
 
-    let server_options: ServerOptions =
-    {
-      run: run,
-      debug: {
-        command: run.command,
-        args: run.args.concat(["-L", path.join(context.extensionPath, "protocol.log")]) }
-    };
+    let server_options: ServerOptions = { run: run, debug: run };
     let client_options: LanguageClientOptions = {
       documentSelector: ["isabelle", "isabelle-ml"]
     };