Using internal functions from CodecBzip2

[nhz2]

For example:

HDF5.jl/ext/CodecBzip2Ext/CodecBzip2Ext.jl

Line 55 in ebaaeee

ret = CodecBzip2.decompress_init!(stream, 0, false)

decompress_init! is not part of CodecBzip2's API and is not documented or tested in CodecBzip2, so using it here may break any time CodecBzip2 is updated.

[mkitti]

These are basically direct translations from C, so perhaps it would be better to depend on the JLLs directly rather than the light wrappers in the codec packages.

However, my hope is that we could eventually replace these direct ports from C with implementations using TranscodingStreams.jl API.