patch 8.1.0389: :behave command is not tested

Problem:    :behave command is not tested.
Solution:   Add a test. (Dominique Pelle, closes #3429)
diff --git a/src/Make_all.mak b/src/Make_all.mak
index 79b8b94..8f0f4c1 100644
--- a/src/Make_all.mak
+++ b/src/Make_all.mak
@@ -14,6 +14,7 @@
 	test_autoload \
 	test_backspace_opt \
 	test_backup \
+	test_behave \
 	test_blockedit \
 	test_breakindent \
 	test_bufline \