lib-compression: Added initial support for LZ4 There's no standard file format for LZ4, so we created our own. The code has had only minimal testing currently, so there may be bugs.

lib-compression: Added support for liblzma (xz) Annoyingly this is mainly copy&pasted [io]stream-bzlib, but I'm not sure if it's worth the effort to try to create common functions for them.

Moved zlib/bzlib code to lib-compression library.