fix offsetof on PHP 8.6+

reference:
php/php-src@7114314

Author: pavetheway91

php_memcached.c

@@ -195,7 +195,7 @@ typedef struct {
 } php_memc_result_callback_ctx_t;
 
 static inline php_memc_object_t *php_memc_fetch_object(zend_object *obj) {
-	return (php_memc_object_t *)((char *)obj - XtOffsetOf(php_memc_object_t, zo));
+	return (php_memc_object_t *)((char *)obj - offsetof(php_memc_object_t, zo));
 }
 #define Z_MEMC_OBJ_P(zv) php_memc_fetch_object(Z_OBJ_P(zv));
 
@@ -280,7 +280,7 @@ typedef struct {
 } php_memc_server_t;
 
 static inline php_memc_server_t *php_memc_server_fetch_object(zend_object *obj) {
-	return (php_memc_server_t *)((char *)obj - XtOffsetOf(php_memc_server_t, zo));
+	return (php_memc_server_t *)((char *)obj - offsetof(php_memc_server_t, zo));
 }
 #define Z_MEMC_SERVER_P(zv) php_memc_server_fetch_object(Z_OBJ_P(zv))
 
@@ -4404,7 +4404,7 @@ PHP_MINIT_FUNCTION(memcached)
 	zend_class_entry ce;
 
 	memcpy(&memcached_object_handlers, zend_get_std_object_handlers(), sizeof(zend_object_handlers));
-	memcached_object_handlers.offset    = XtOffsetOf(php_memc_object_t, zo);
+	memcached_object_handlers.offset    = offsetof(php_memc_object_t, zo);
 	memcached_object_handlers.clone_obj = NULL;
 	memcached_object_handlers.free_obj  = php_memc_object_free_storage;
 
@@ -4415,7 +4415,7 @@ PHP_MINIT_FUNCTION(memcached)
 
 #ifdef HAVE_MEMCACHED_PROTOCOL
 	memcpy(&memcached_server_object_handlers, zend_get_std_object_handlers(), sizeof(zend_object_handlers));
-	memcached_server_object_handlers.offset = XtOffsetOf(php_memc_server_t, zo);
+	memcached_server_object_handlers.offset = offsetof(php_memc_server_t, zo);
 	memcached_server_object_handlers.clone_obj = NULL;
 	memcached_server_object_handlers.free_obj = php_memc_server_free_storage;