deps: Update to itoa 1.

In itoa 1, the interface has been slimmed down and the fmt method
is no longer present, so expand to the code that was there previously.

Cargo.toml

@@ -26,7 +26,7 @@ rust-version = "1.46.0"
 [dependencies]
 bytes = "1"
 fnv = "1.0.5"
-itoa = "0.4.1"
+itoa = "1"
 
 [dev-dependencies]
 indexmap = "1.0"

src/header/value.rs

@@ -2,6 +2,7 @@ use bytes::{Bytes, BytesMut};
 
 use std::convert::TryFrom;
 use std::error::Error;
+use std::fmt::Write;
 use std::str::FromStr;
 use std::{cmp, fmt, mem, str};
 
@@ -427,7 +428,7 @@ macro_rules! from_integers {
                     // full value fits inline, so don't allocate!
                     BytesMut::new()
                 };
-                let _ = ::itoa::fmt(&mut buf, num);
+                let _ = buf.write_str(::itoa::Buffer::new().format(num));
                 HeaderValue {
                     inner: buf.freeze(),
                     is_sensitive: false,