patch 8.1.1004: function "luaV_setref()" not covered with tests

Problem:    Function "luaV_setref()" not covered with tests.
Solution:   Add a test. (Dominique Pelle, closes #4089)
diff --git a/src/version.c b/src/version.c
index 5b16760..0b0ab0c 100644
--- a/src/version.c
+++ b/src/version.c
@@ -780,6 +780,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1004,
+/**/
     1003,
 /**/
     1002,