add Noop node

src/babel/generation/generators/base.js

@@ -17,3 +17,7 @@ export function BlockStatement(node, print) {
     this.rightBrace();
   }
 }
+
+export function Noop() {
+
+}

src/babel/patch.js

@@ -17,6 +17,8 @@ var or  = types.Type.or;
 //  .build("program")
 //  .field("program", def("Program"));
 
+def("Noop");
+
 def("AssignmentPattern")
   .bases("Pattern")
   .build("left", "right")

src/babel/types/visitor-keys.json

@@ -43,6 +43,7 @@
   "MetaProperty":              ["meta", "property"],
   "MethodDefinition":          ["key", "value", "decorators"],
   "NewExpression":             ["callee", "arguments"],
+  "Noop":                      [],
   "ObjectExpression":          ["properties"],
   "ObjectPattern":             ["properties", "typeAnnotation"],
   "Program":                   ["body"],