use skynet malloc api directly

skynet-src/skynet_error.c

@@ -34,14 +34,14 @@ skynet_error(struct skynet_context * context, const char *msg, ...) {
 		int max_size = LOG_MESSAGE_SIZE;
 		for (;;) {
 			max_size *= 2;
-			data = malloc(max_size);
+			data = skynet_malloc(max_size);
 			va_start(ap,msg);
 			len = vsnprintf(data, max_size, msg, ap);
 			va_end(ap);
 			if (len < max_size) {
 				break;
 			}
-			free(data);
+			skynet_free(data);
 		}
 	}