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/indent.txt b/runtime/doc/indent.txt
index 6e8f35b..69a03f9 100644
--- a/runtime/doc/indent.txt
+++ b/runtime/doc/indent.txt
@@ -42,11 +42,12 @@
 that toplevel functions have a '{' in the first column.  Otherwise they are
 easily confused with declarations.
 
-These four options control C program indenting:
+These five options control C program indenting:
 'cindent'	Enables Vim to perform C program indenting automatically.
 'cinkeys'	Specifies which keys trigger reindenting in insert mode.
 'cinoptions'	Sets your preferred indent style.
 'cinwords'	Defines keywords that start an extra indent in the next line.
+'cinscopedecls'	Defines strings that are recognized as a C++ scope declaration.
 
 If 'lisp' is not on and 'equalprg' is empty, the "=" operator indents using
 Vim's built-in algorithm rather than calling an external program.
@@ -293,8 +294,9 @@
 <
 							*cino-g*
 	gN    Place C++ scope declarations N characters from the indent of the
-	      block they are in.  (default 'shiftwidth').  A scope declaration
-	      can be "public:", "protected:" or "private:".
+	      block they are in.  (default 'shiftwidth'). By default, a scope 
+	      declaration is "public:", "protected:" or "private:". This can
+	      be adjusted with the 'cinscopedecls' option.
 
 		cino=		    cino=g0 >
 		  {		      {