make comments output more robust (#2633)

- improve handling of comments right after `return`
- retain comments after `OutputStream`
- preserve trailing comments
- fix handling of new line before comments
- handle comments around parentheses

fixes #88
fixes #112
fixes #218
fixes #372
fixes #2629

lib/ast.js

@@ -87,7 +87,7 @@ function DEFNODE(type, props, methods, base) {
     return ctor;
 };
 
-var AST_Token = DEFNODE("Token", "type value line col pos endline endcol endpos nlb comments_before file raw", {
+var AST_Token = DEFNODE("Token", "type value line col pos endline endcol endpos nlb comments_before comments_after file raw", {
 }, null);
 
 var AST_Node = DEFNODE("Node", "start end", {