httpserver: use own HTTP status codes

Before, macros defined in `<event2/http.h>` have been used
for some HTTP status codes.
`<event2/http.h>` is included implicitly and the usage
of its status code macros is inconsistent with the majority
HTTP response implementations in this file.

Now, the `HTTPStatusCode` enum from `<rpc/protocol.h>` is
consistently used for all HTTP response implementations.

Author: toxeus

src/httpserver.cpp

@@ -236,7 +236,7 @@ static void http_request_cb(struct evhttp_request* req, void* arg)
     if (hreq->GetRequestMethod() == HTTPRequest::UNKNOWN) {
         LogPrint(BCLog::HTTP, "HTTP request from %s rejected: Unknown HTTP request method\n",
                  hreq->GetPeer().ToString());
-        hreq->WriteReply(HTTP_BADMETHOD);
+        hreq->WriteReply(HTTP_BAD_METHOD);
         return;
     }
 
@@ -268,10 +268,10 @@ static void http_request_cb(struct evhttp_request* req, void* arg)
             item.release(); /* if true, queue took ownership */
         else {
             LogPrintf("WARNING: request rejected because http work queue depth exceeded, it can be increased with the -rpcworkqueue= setting\n");
-            item->req->WriteReply(HTTP_INTERNAL, "Work queue depth exceeded");
+            item->req->WriteReply(HTTP_INTERNAL_SERVER_ERROR, "Work queue depth exceeded");
         }
     } else {
-        hreq->WriteReply(HTTP_NOTFOUND);
+        hreq->WriteReply(HTTP_NOT_FOUND);
     }
 }
 
@@ -519,7 +519,7 @@ HTTPRequest::~HTTPRequest()
     if (!replySent) {
         // Keep track of whether reply was sent to avoid request leaks
         LogPrintf("%s: Unhandled request\n", __func__);
-        WriteReply(HTTP_INTERNAL, "Unhandled request");
+        WriteReply(HTTP_INTERNAL_SERVER_ERROR, "Unhandled request");
     }
     // evhttpd cleans up the request, as long as a reply was sent.
 }