Adjust error message, now that we expect other message types than connection

close at this point. Fix PQsetnonblocking() comment.

Fujii Masao

src/backend/replication/walsender.c

@@ -506,7 +506,7 @@ ProcessRepliesIfAny(void)
 			default:
 				ereport(FATAL,
 						(errcode(ERRCODE_PROTOCOL_VIOLATION),
-						 errmsg("invalid standby closing message type %d",
+						 errmsg("invalid standby message type %d",
 								firstchar)));
 		}
 	}