patch 7.4.741
Problem:    When using += with ":set" a trailing comma is not recognized.
            (Issue 365)
Solution:   Don't add a second comma. Add a test. (partly by Christian
            Brabandt)
diff --git a/src/testdir/Make_dos.mak b/src/testdir/Make_dos.mak
index 787d76e..1eec9d7 100644
--- a/src/testdir/Make_dos.mak
+++ b/src/testdir/Make_dos.mak
@@ -53,6 +53,7 @@
 		test_nested_function.out \
 		test_options.out \
 		test_qf_title.out \
+		test_set.out \
 		test_signs.out \
 		test_textobjects.out \
 		test_utf8.out