[client.keyset] added Getter and Setter 'MigrationCode(<uint8|nil>) uint8' for migration code

src/git.xdrm.io/schastsp/client/keyset/keyset.go

@@ -183,3 +183,26 @@ func (s *T) Fetch(reader io.Reader) error {
 	return nil
 
 }
+
+
+/* (6) Getter/Setter for migration code 'mcode'
+*
+* @mcode<uint8>					[OPT] New value
+*
+* @return mcode<uint8>			Migration code
+*
+---------------------------------------------------------*/
+func (s T) MigrationCode(optional... uint8) uint8 {
+
+	/* (1) If no valid code given -> return current one */
+	if len(optional) < 1 || optional[0] > 3 {
+		return s.mcode
+	}
+
+	/* (2) Set new code */
+	s.mcode = optional[0]
+
+	/* (3) Return new code */
+	return s.mcode
+
+}