patch 8.2.3233: prop_list() and prop_find() do not indicate the buffer

Problem:    prop_list() and prop_find() do not indicate the buffer for the
            used type.
Solution:   Add "type_bufnr" to the results. (closes #8647)

runtime/doc/textprop.txt

@@ -211,6 +211,8 @@ prop_list({lnum} [, {props}])				*prop_list()*
 		   id		property ID
 		   type		name of the property type, omitted if
 				the type was deleted
+		   type_bufnr	buffer number for which this type was defined;
+				0 if the type is global
 		   start	when TRUE property starts in this line
 		   end		when TRUE property ends in this line