feat: deprecate @angular/http in favor of @angular/common/http (#18906)

As of 5.0, @angular/http is deprecated. @angular/common/http will
be the official HTTP API in Angular going forward.

PR Close #18906

packages/http/src/version.ts

@@ -14,6 +14,6 @@
 
 import {Version} from '@angular/core';
 /**
- * @stable
+ * @deprecated use @angular/common/http instead
  */
 export const VERSION = new Version('0.0.0-PLACEHOLDER');