Add ReturnTypeWillChange to JsonSerializable implementation
Add ReturnTypeWillChange to JsonSerializable implementation

Signed-off-by: Alexander M. Turek <b1c1d8736f20db3fb6c1c66bb1455ed43909f0d8@derrabus.de>

twigphp/Twig,twigphp/Twig,twigphp/Twig