doc: http: add cross-links for easier clicking

Make it a little easier to navigate the http module documentation by
turning class names and methods into links to the appropriate section.

doc/api/http.markdown

@@ -56,8 +56,8 @@ This is an [EventEmitter][] with the following events:
 
 Emitted each time there is a request. Note that there may be multiple requests
 per connection (in the case of keep-alive connections).
- `request` is an instance of `http.IncomingMessage` and `response` is
- an instance of `http.ServerResponse`
+ `request` is an instance of [http.IncomingMessage][] and `response` is
+an instance of [http.ServerResponse][].
 
 ### Event: 'connection'
 
@@ -83,7 +83,7 @@ Emitted each time a request with an http Expect: 100-continue is received.
 If this event isn't listened for, the server will automatically respond
 with a 100 Continue as appropriate.
 
-Handling this event involves calling `response.writeContinue` if the client
+Handling this event involves calling [response.writeContinue()][] if the client
 should continue to send the request body, or generating an appropriate HTTP
 response (e.g., 400 Bad Request) if the client should not continue to send the
 request body.
@@ -233,7 +233,7 @@ The response implements the [Writable Stream][] interface. This is an
 `function () { }`
 
 Indicates that the underlying connection was terminated before
-`response.end()` was called or able to flush.
+[response.end()][] was called or able to flush.
 
 ### response.writeContinue()
 
@@ -255,9 +255,9 @@ Example:
       'Content-Type': 'text/plain' });
 
 This method must only be called once on a message and it must
-be called before `response.end()` is called.
+be called before [response.end()][] is called.
 
-If you call `response.write()` or `response.end()` before calling this, the
+If you call [response.write()][] or [response.end()][] before calling this, the
 implicit/mutable headers will be calculated and call this function for you.
 
 Note: that Content-Length is given in bytes not characters. The above example
@@ -284,9 +284,9 @@ sockets.
 
 ### response.statusCode
 
-When using implicit headers (not calling `response.writeHead()` explicitly), this property
-controls the status code that will be sent to the client when the headers get
-flushed.
+When using implicit headers (not calling [response.writeHead()][] explicitly),
+this property controls the status code that will be sent to the client when
+the headers get flushed.
 
 Example:
 
@@ -342,8 +342,8 @@ Example:
 
 ### response.write(chunk, [encoding])
 
-If this method is called and `response.writeHead()` has not been called, it will
-switch to implicit header mode and flush the implicit headers.
+If this method is called and [response.writeHead()][] has not been called,
+it will switch to implicit header mode and flush the implicit headers.
 
 This sends a chunk of the response body. This method may
 be called multiple times to provide successive parts of the body.
@@ -424,7 +424,7 @@ Options:
  - `false`: opts out of connection pooling with an Agent, defaults request to
    `Connection: close`.
 
-`http.request()` returns an instance of the `http.ClientRequest`
+`http.request()` returns an instance of the [http.ClientRequest][]
 class. The `ClientRequest` instance is a writable stream. If one needs to
 upload a file with a POST request, then write to the `ClientRequest` object.
 
@@ -556,7 +556,7 @@ data chunk or when closing the connection.
 To get the response, add a listener for `'response'` to the request object.
 `'response'` will be emitted from the request object when the response
 headers have been received.  The `'response'` event is executed with one
-argument which is an instance of `http.IncomingMessage`.
+argument which is an instance of [http.IncomingMessage][].
 
 During the `'response'` event, one can add listeners to the
 response object; particularly to listen for the `'data'` event.
@@ -581,7 +581,7 @@ The request implements the [Writable Stream][] interface. This is an
 `function (response) { }`
 
 Emitted when a response is received to this request. This event is emitted only
-once. The `response` argument will be an instance of `http.IncomingMessage`.
+once. The `response` argument will be an instance of [http.IncomingMessage][].
 
 Options:
 
@@ -760,9 +760,10 @@ Once a socket is assigned to this request and is connected
 
 ## http.IncomingMessage
 
-An `IncomingMessage` object is created by `http.Server` or `http.ClientRequest`
-and passed as the first argument to the `'request'` and `'response'` event
-respectively. It may be used to access response status, headers and data.
+An `IncomingMessage` object is created by [http.Server][] or
+[http.ClientRequest][] and passed as the first argument to the `'request'`
+and `'response'` event respectively. It may be used to access response status,
+headers and data.
 
 It implements the [Readable Stream][] interface, as well as the
 following additional events, methods, and properties.
@@ -813,14 +814,14 @@ Calls `message.connection.setTimeout(msecs, callback)`.
 
 ### message.method
 
-**Only valid for request obtained from `http.Server`.**
+**Only valid for request obtained from [http.Server][].**
 
 The request method as a string. Read only. Example:
 `'GET'`, `'DELETE'`.
 
 ### message.url
 
-**Only valid for request obtained from `http.Server`.**
+**Only valid for request obtained from [http.Server][].**
 
 Request URL string. This contains only the URL that is
 present in the actual HTTP request. If the request is:
@@ -867,21 +868,29 @@ request.connection.getPeerCertificate() to obtain the client's
 authentication details.
 
 
-[Agent]: #http_class_http_agent
 ['checkContinue']: #http_event_checkcontinue
+['listening']: net.html#net_event_listening
+[Agent]: #http_class_http_agent
 [Buffer]: buffer.html#buffer_buffer
 [EventEmitter]: events.html#events_class_events_eventemitter
+[Readable Stream]: stream.html#stream_readable_stream
+[Writable Stream]: stream.html#stream_writable_stream
 [global Agent]: #http_http_globalagent
+[http.ClientRequest]: #http_class_http_clientrequest
+[http.IncomingMessage]: #http_http_incomingmessage
+[http.ServerResponse]: #http_class_http_serverresponse
+[http.Server]: #http_class_http_server
+[http.request()]: #http_http_request_options_callback
 [http.request()]: #http_http_request_options_callback
-[http.IncomingMessage]: #http_class_http_incomingmessage
-['listening']: net.html#net_event_listening
 [net.Server.close()]: net.html#net_server_close_callback
 [net.Server.listen(path)]: net.html#net_server_listen_path_callback
 [net.Server.listen(port)]: net.html#net_server_listen_port_host_backlog_callback
-[Readable Stream]: stream.html#stream_readable_stream
+[response.end()]: #http_response_end_data_encoding
+[response.write()]: #http_response_write_chunk_encoding
+[response.writeContinue()]: #http_response_writecontinue
+[response.writeHead()]: #http_response_writehead_statuscode_reasonphrase_headers
 [socket.setKeepAlive()]: net.html#net_socket_setkeepalive_enable_initialdelay
 [socket.setNoDelay()]: net.html#net_socket_setnodelay_nodelay
 [socket.setTimeout()]: net.html#net_socket_settimeout_timeout_callback
 [stream.setEncoding()]: stream.html#stream_stream_setencoding_encoding
 [url.parse()]: url.html#url_url_parse_urlstr_parsequerystring_slashesdenotehost
-[Writable Stream]: stream.html#stream_writable_stream