chore(docs): rename @private to @internal

The latter is understood by TypeScript's --stripInternal option, so this lets us
rely more on the tooling provided by typescript team.

modules/angular2/src/http/backends/jsonp_backend.ts

@@ -21,7 +21,7 @@ export class JSONPConnection implements Connection {
   private _finished: boolean = false;
 
   /**
-   * @private
+   * @internal
    */
   constructor(req: Request, private _dom: BrowserJsonp,
               private baseResponseOptions?: ResponseOptions) {
@@ -103,7 +103,7 @@ export class JSONPConnection implements Connection {
 @Injectable()
 export class JSONPBackend implements ConnectionBackend {
   /**
-   * @private
+   * @internal
    */
   constructor(private _browserJSONP: BrowserJsonp, private _baseResponseOptions: ResponseOptions) {}
   createConnection(request: Request): JSONPConnection {

modules/angular2/src/http/base_response_options.ts

@@ -46,11 +46,11 @@ export class ResponseOptions {
    */
   headers: Headers;
   /**
-   * @private
+   * @internal
    */
   statusText: string;
   /**
-   * @private
+   * @internal
    */
   type: ResponseTypes;
   url: string;