Update the docs to include old_value

lib/Jifty/DBI/Record.pm

@@ -733,10 +733,10 @@ for every column set.
 
 This hook will be called after a value is successfully set in the
 database. It will be called with a reference to a paramhash that
-contains C<column> and C<value> keys. If C<value> was a SQL function,
-it will now contain the actual value that was set. If C<column> has
-filters on it, C<value> will be the result of going through an encode
-and decode cycle.
+contains C<column>, C<value>, and C<old_value> keys. If C<value> was a
+SQL function, it will now contain the actual value that was set. If
+C<column> has filters on it, C<value> will be the result of going
+through an encode and decode cycle.
 
 This hook's return value is ignored.