Moved docgen out of the sdk into pkg/

sdk/lib/_internal/docgen/examples/test.dart

-/**
- * This library is used solely for testing during development and is not
- * intended to be run by the testing machines.
- */
-// TODO(tmandel): Remove this file once docgen is ready for more clear tests.
-library DummyLibrary;
-
-import 'dart:json';
-import 'dart:math';
-
-/// Doc comment for top-level variable.
-int _variable1 = 0;
-
-void set variable1(int abc) => _variable1 = abc;
-
-abstract class B {
-
-}
-
-/**
- * Doc comment for class A.
- */
-/*
- * Normal comment for class A.
- */
-class A implements B {
-
-  /**
-   * Markdown _test_ for **class** `A` 
-   */
-  int _someNumber;
-
-  A() {
-    _someNumber = 12;
-  }
-
-  int get someNumber => _someNumber;
-
-  void doThis(int a) {
-    print(a);
-  }
-
-  int multi(int a) {
-    return a * _someNumber;
-  } 
-
-}
-
-main() {
-  A a = new A();
-  print(a.someNumber);
-}
-
-A getA(int testInt, [String testString="default"]) {
-  return new A();
-}