patch 8.1.1803: all builtin functions are global

Problem:    All builtin functions are global.
Solution:   Add the method call operator ->.  Implemented for a limited number
            of functions.
diff --git a/src/testdir/Make_all.mak b/src/testdir/Make_all.mak
index a0898dc..b3abcba 100644
--- a/src/testdir/Make_all.mak
+++ b/src/testdir/Make_all.mak
@@ -180,6 +180,7 @@
 	test_matchadd_conceal \
 	test_matchadd_conceal_utf8 \
 	test_memory_usage \
+	test_method \
 	test_menu \
 	test_messages \
 	test_mksession \
@@ -373,6 +374,7 @@
 	test_marks.res \
 	test_matchadd_conceal.res \
 	test_memory_usage.res \
+	test_method.res \
 	test_mksession.res \
 	test_nested_function.res \
 	test_netbeans.res \