Added basic HTTP request processing in router.

- request to connection mapping in engine;
- requests queue in connection;
- engine port creation;
- connected ports hash for each process;
- engine port data messages processing (app responses);

src/nxt_event_engine.h

@@ -491,6 +491,7 @@ struct nxt_event_engine_s {
     nxt_queue_t                joints;
     nxt_queue_t                listen_connections;
     nxt_queue_t                idle_connections;
+    nxt_lvlhsh_t               requests; /* req_id to nxt_req_conn_link_t */
 
     nxt_queue_link_t           link;
 };
@@ -509,6 +510,15 @@ NXT_EXPORT void nxt_event_engine_post(nxt_event_engine_t *engine,
 NXT_EXPORT void nxt_event_engine_signal(nxt_event_engine_t *engine,
     nxt_uint_t signo);
 
+NXT_EXPORT void nxt_event_engine_request_add(nxt_event_engine_t *engine,
+    nxt_req_conn_link_t *rc);
+NXT_EXPORT nxt_req_conn_link_t *nxt_event_engine_request_find(
+    nxt_event_engine_t *engine, nxt_req_id_t req_id);
+NXT_EXPORT void nxt_event_engine_request_remove(nxt_event_engine_t *engine,
+    nxt_req_conn_link_t *rc);
+NXT_EXPORT nxt_req_conn_link_t *nxt_event_engine_request_find_remove(
+    nxt_event_engine_t *engine, nxt_req_id_t req_id);
+
 
 nxt_inline nxt_event_engine_t *
 nxt_thread_event_engine(void)