patch 8.2.0968: no proper testing of the 'cpoptions' flags

Problem:    No proper testing of the 'cpoptions' flags.
Solution:   Add tests. (Yegappan Lakshmanan, closes #6251)
diff --git a/src/testdir/Make_all.mak b/src/testdir/Make_all.mak
index 2a133ef..3d14358 100644
--- a/src/testdir/Make_all.mak
+++ b/src/testdir/Make_all.mak
@@ -94,6 +94,7 @@
 	test_compiler \
 	test_conceal \
 	test_const \
+	test_cpoptions \
 	test_crypt \
 	test_cscope \
 	test_cursor_func \
@@ -343,6 +344,7 @@
 	test_comparators.res \
 	test_conceal.res \
 	test_const.res \
+	test_cpoptions.res \
 	test_crypt.res \
 	test_cscope.res \
 	test_cursor_func.res \