Reimplementation, MacOS support

This is a complete reimplementation of the project to make it buildable on modern computers. It now supports MacOS in addition to Linux (and maybe others), and has basic support for disassembling x86, ARM and (to some extent) AARCH64.

This release should be usable, but is more of a foundation for future work. In particular, architecture identification when binutils-multiarch isn't used should be improved.