patch 8.2.4702: C++ scope labels are hard-coded

Problem:    C++ scope labels are hard-coded.
Solution:   Add 'cinscopedecls' to define the labels. (Rom Praschan,
            closes #10109)
diff --git a/src/optionstr.c b/src/optionstr.c
index 09e6d8a..fd72da4 100644
--- a/src/optionstr.c
+++ b/src/optionstr.c
@@ -260,6 +260,7 @@
 #ifdef FEAT_CINDENT
     check_string_option(&buf->b_p_cink);
     check_string_option(&buf->b_p_cino);
+    check_string_option(&buf->b_p_cinsd);
     parse_cino(buf);
 #endif
     check_string_option(&buf->b_p_ft);