Compression threshold depending on shuffle active?

Perhaps it would be nice to study whether the compression thresholds in blosclz.c should depend on whether shuffle is active or not, in addition to the compression level.

Start by reading blosclz.c, focusing on the compression thresholds and how shuffle activity and compression level are handled. Determine whether shuffle-dependent thresholds are needed and define the expected behavior and tests before considering an implementation.

Written by the indexing model from the issue text.