MEDIUM: checks: Add status-code sample expression on tcp-check expect rules

This option defines a sample expression, evaluated as an integer, to set the
status code (check->code) if a tcp-check healthcheck ends on the corresponding
expect rule.
diff --git a/include/types/checks.h b/include/types/checks.h
index 0d479e3..3c44d82 100644
--- a/include/types/checks.h
+++ b/include/types/checks.h
@@ -268,6 +268,7 @@
 	struct list onsuccess_fmt;      /* log-format string to use as comment on success (if last rule) */
 	enum healthcheck_status err_status;  /* The healthcheck status to use on error (default: L7RSP) */
 	enum healthcheck_status tout_status; /* The healthcheck status to use on timeout (default: L7TOUT) */
+	struct sample_expr *status_expr; /* sample expr to determine the check status code */
 };
 
 struct tcpcheck_action_kw {