doc: fix named anchors in addons.markdown and http.markdown

PR-URL: https://github.com/nodejs/node/pull/4708
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

doc/api/addons.markdown

@@ -1018,5 +1018,5 @@ Test in JavaScript by running:
 [Native Abstrations for Node.js]: https://github.com/nodejs/nan
 [examples]: https://github.com/nodejs/nan/tree/master/examples/
 [bindings]: https://github.com/TooTallNate/node-bindings
-[Linking to Node.js' own dependencies]: #linking-to-node-js-own-dependencies
+[Linking to Node.js' own dependencies]: #linking-to-nodejs-own-dependencies
 [installation instructions]: https://github.com/nodejs/node-gyp#installation

doc/api/http.markdown

@@ -1112,7 +1112,7 @@ There are a few special headers that should be noted.
 [`http.Agent`]: #http_class_http_agent
 [`http.ClientRequest`]: #http_class_http_clientrequest
 [`http.globalAgent`]: #http_http_globalagent
-[`http.IncomingMessage`]: #http_http_incomingmessage
+[`http.IncomingMessage`]: #http_class_http_incomingmessage
 [`http.request()`]: #http_http_request_options_callback
 [`http.Server`]: #http_class_http_server
 [`http.ServerResponse`]: #http_class_http_serverresponse