-improve version checking

class-wc-gnutaler-gateway.php

@@ -42,7 +42,7 @@ define( 'GNU_TALER_MERCHANT_PROTOCOL_CURRENT', 3 );
 /**
  * How many merchant protocol versions are we backwards compatible with?
  */
-define( 'GNU_TALER_MERCHANT_PROTOCOL_AGE', 2 );
+define( 'GNU_TALER_MERCHANT_PROTOCOL_AGE', 0 );
 
 require_once ABSPATH . 'wp-admin/includes/plugin.php';
 
@@ -549,7 +549,8 @@ function gnutaler_init_gateway_class() {
 					$age      = $ver[2];
 					if ( ( ! is_numeric( $current ) )
 						 || ( ! is_numeric( $revision ) )
-						 || ( ! is_numeric( $age ) )
+						 || ( ! is_numeric( $age )
+						 || ( $age > $current ) )
 					   ) {
 						$this->error(
 							sprintf(
@@ -583,7 +584,8 @@ function gnutaler_init_gateway_class() {
 						return false;
 					}
 					$currency = $info['currency'];
-					if ( ( ! is_null( $ecurrency ) ) && ( 0 !== strcasecmp( $currency, $ecurrency ) ) ) {
+					if ( ( ! is_null( $ecurrency ) ) &&
+					     ( 0 !== strcasecmp( $currency, $ecurrency ) ) ) {
 						$this->error(
 							sprintf(
 								/* translators: first placeholder is the Taler backend currency, second the expected currency from WooCommerce */