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/option.c b/src/option.c
index 4d50a64..49123aa 100644
--- a/src/option.c
+++ b/src/option.c
@@ -5449,6 +5449,7 @@
 	case PV_CIN:	return (char_u *)&(curbuf->b_p_cin);
 	case PV_CINK:	return (char_u *)&(curbuf->b_p_cink);
 	case PV_CINO:	return (char_u *)&(curbuf->b_p_cino);
+	case PV_CINSD:	return (char_u *)&(curbuf->b_p_cinsd);
 #endif
 #if defined(FEAT_SMARTINDENT) || defined(FEAT_CINDENT)
 	case PV_CINW:	return (char_u *)&(curbuf->b_p_cinw);
@@ -6020,6 +6021,8 @@
 	    COPY_OPT_SCTX(buf, BV_CINK);
 	    buf->b_p_cino = vim_strsave(p_cino);
 	    COPY_OPT_SCTX(buf, BV_CINO);
+	    buf->b_p_cinsd = vim_strsave(p_cinsd);
+	    COPY_OPT_SCTX(buf, BV_CINSD);
 #endif
 	    // Don't copy 'filetype', it must be detected
 	    buf->b_p_ft = empty_option;