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/runtime/doc/quickref.txt b/runtime/doc/quickref.txt
index e532942..279e3d5 100644
--- a/runtime/doc/quickref.txt
+++ b/runtime/doc/quickref.txt
@@ -643,6 +643,7 @@
 'cinkeys'	  'cink'    keys that trigger indent when 'cindent' is set
 'cinoptions'	  'cino'    how to do indenting when 'cindent' is set
 'cinwords'	  'cinw'    words where 'si' and 'cin' add an indent
+'cinscopedecls'	  'cinsd'   words that are recognized by 'cino-g' 
 'clipboard'	  'cb'	    use the clipboard as the unnamed register
 'cmdheight'	  'ch'	    number of lines to use for the command-line
 'cmdwinheight'	  'cwh'     height of the command-line window