Constant io_interner::BUF_LEN

pub const BUF_LEN: usize = 512;

Internal buffer length used in many free functions of this crate,put here if in the future some way of create it at compile time it’s implemented,only thinkable way it’s option_env!("IOINTERNER_BUF_LEN").and_then(|e| e.trim().parse().ok()).unwrap_or(512) but, except for option_env! and Option::{and_then, unwrap_or},cannot be put into a constant.