Disabling the `std` feature (by setting `default-features = false` for
this crate in the Cargo.toml of something requiring it) will enable the
crate to work without the standard library, assuming the presence of
the `alloc` crate and a working global allocator.
We've explicitly imported the individual `alloc` items required by this
crate, rather than using `#![feature(alloc_prelude)]` as `alloc_prelude`
requires Rust nightly, and doing it that way would be a breaking change
to the MSRV.
Tested with Cargo/rustc 1.53.0
Fenhl