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/structs.h b/src/structs.h
index 5a76a59..a1dbfbe 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -2881,6 +2881,7 @@
     int		b_p_cin;	// 'cindent'
     char_u	*b_p_cino;	// 'cinoptions'
     char_u	*b_p_cink;	// 'cinkeys'
+    char_u	*b_p_cinsd;	// 'cinscopedecls'
 #endif
 #if defined(FEAT_CINDENT) || defined(FEAT_SMARTINDENT)
     char_u	*b_p_cinw;	// 'cinwords'