Improved addcslashes parameters charlist length control in 256 bytes

Strictly speaking, addcslashes charlist parameter 256-byte is enough.And in the php_charmask function is  Fills a 256-byte bytemask with input
1. why? does it hurt?
2. if it's E_DEPERCATED, why return false below. deprecated should just be a warning. you should not change the behavior.