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)
diff --git a/runtime/doc/textprop.txt b/runtime/doc/textprop.txt
index c134290..52191ae 100644
--- a/runtime/doc/textprop.txt
+++ b/runtime/doc/textprop.txt
@@ -211,6 +211,8 @@
 		   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