Keep C version forever, alongside Rust version

Please keep a maintained, secure version of bzip2 around written in C. Even if it isn't the best code possible, many systems need bzip2 around that cannot build nor utilise Rust.

Some of these include:

• AIX (no definitions)
• Linux/Alpha (no definitions, no CPU support)
• Linux/RISC-V (core-only bare metal target, no std)
• OpenBSD (tier 3, unsupported)
• QNX (no definitions, definitely no std)
• and others...

As the lead of a Linux distribution, I have seen firsthand the trials of bootstrapping Rust on a new platform. As an example, Rust did not support PowerPC musl Linux at all, and it's taken us almost two years to even get a building compiler (let alone a working one). I implore you to continue to support a bzip2 written in C for this reason. Thank you for your consideration.