Python WSGI: SERVER_NAME, SERVER_PORT fixed, REMOTE_ADDR introduced.

Shortcut: do not iterate over String (or Bytes) return object.
Call 'close()' for return object (if present).

src/nxt_application.h

@@ -43,6 +43,8 @@ typedef struct {
 typedef struct {
     nxt_app_request_header_t   header;
     nxt_app_request_body_t     body;
+
+    nxt_str_t                  remote;
 } nxt_app_request_t;