patch 8.2.4668: buffer allocation failures insufficiently tested

Problem:    Buffer allocation failures insufficiently tested.
Solution:   Add tests for memory allocation failures. (Yegappan Lakshmanan,
            closes #10064)
diff --git a/src/alloc.h b/src/alloc.h
index 9260018..35c00b6 100644
--- a/src/alloc.h
+++ b/src/alloc.h
@@ -40,5 +40,6 @@
     aid_sign_getplaced_list,
     aid_insert_sign,
     aid_sign_getinfo,
+    aid_buflistnew_bvars,
     aid_last
 } alloc_id_T;