Add parallelized compression

[mxmlnkn]

The most difficult part is probably the build system and packaging because currently only the files necessaryfor decompression from zlib and ISA-l are built and packaged.

Aside from that, simply split the data, send to the ThreadPool, compress and concatenate to the output in the right order.

In the first, iteration, I could simply write out similar to bgzip. In an improvement it would be nice to somehow store the whole index more easily accessible. Maybe similar to the format written by pgzf or gztool.

This would be nice for rapidgzip to be usable as a drop-in replacement for gzip.

[ashleysommer]

@mxmlnkn
Do you still have plans to add support for gzip compression to rapidgzip?

[mxmlnkn]

Yeah, it would be nice to have a drop-in replacement for gzip that could compress and decompress, but time is limited. Currently, I am doing some work on ratarmount, and the immediate next goal would be lz4 decompression and the new index format instead. Seeing that this issue is almost 2 years old, this means that this is a very long-term goal, especially as compression with bgzip works reasonably well.

Help would be welcome.