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/options.txt b/runtime/doc/options.txt
index d5e5e68..8b20211 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -1661,13 +1661,23 @@
 	matter, include the keyword both the uppercase and lowercase:
 	"if,If,IF".
 
-						*'clipboard'* *'cb'*
+						*'cinscopedecls'* *'cinsd'*
+'cinscopedecls' 'cinsd'	string	(default "public,protected,private")
+			local to buffer
+			{not available when compiled without the |+cindent|
+			feature}
+	Keywords that are interpreted as a C++ scope declaration by |cino-g|.
+	Useful e.g. for working with the Qt framework that defines additional
+	scope declarations "signals", "public slots" and "private slots": >
+		set cinscopedecls+=signals,public\ slots,private\ slots
+
+<						*'clipboard'* *'cb'*
 'clipboard' 'cb'	string	(default "autoselect,exclude:cons\|linux"
 						  for X-windows, "" otherwise)
 			global
 			{only in GUI versions or when the |+xterm_clipboard|
 			feature is included}
-	This option is a list of comma separated names.
+	This option is a list of comma-separated names.
 	Note: if one of the items is "exclude:", then you can't add an item
 	after that.  Therefore do append an item with += but use ^= to
 	prepend, e.g.: >