bzip2 build system

Sure, happy to merge stuff. Ideally I'd like to hand it to upstream and drop my local patches, as I did for libtiff. While I originally kept this to using CMake 2.8 for greater portability and upstream merging, I might well think about a move to 3.2+ like the rest of the codebase if that's unlikely to happen. Is your version publicly available? Are you mathstuf on github, by the way?

Feel free to snarf any of the superbuild stuff; it's all permissively BSD licensed (as are all my current work projects). You might also want to look at "hunter"; I ended up going my own way since I didn't want to rely on network connectivity to build, and I also needed things building with options not used there, as well as caching downloaded sources. This one is fairly flexible in that you can arbitrarily extend it, and it will recursively resolve dependencies (optional, so you can use the distro-provided ones where available). It will likely get further simplified over time, but hopefully might be useful for inspiration.