Bzip2-sys does not support the value 0 for blockSize100k

[Plecra]

We are directly passing Compression::level to BZ2_bzCompressInit

/~https://github.com/alexcrichton/bzip2-rs/blob/016e18155ef7c05983ea244cae1344c5b68defd8/src/mem.rs#L123-L126

However, this API only supports values from 1..=9 as documented here in the sources

Parameter blockSize100k specifies the block size to be used for compression. It should be a value between 1 and 9 inclusive, and the actual block size used is 100000 x this figure. 9 gives the best compression but takes most memory.

This bug seems to have been introduced in #37, where we tried to support an API aligned with flate2::Compression. However, our version of Compression::none will always panic on the above assertion with BZ_PARAM_ERROR

/~https://github.com/alexcrichton/bzip2-rs/blob/016e18155ef7c05983ea244cae1344c5b68defd8/src/lib.rs#L100-L102

References

We had a panic in usage of zip over here :) zip-rs/zip-old#326

Suggestions

As the library doesnt appear to support disabling compression, I would prefer none to be deprecated, and a bounds check to be added to Compression::new. Hopefully there's a clean way to provide the equivalent of flate2's none and we can specifically branch on 0?