Mega-PR for fixing compilation on Haiku

For [this](https://www.google-melange.com/gci/task/view/google/gci2013/5909642936844288) task.

This PR will house all my commits so you can check my work in progress and I have a comprehensive history in case I need to revert to something. When the task's done, I'll squash all my commits into one so that it looks nice in the commit history.

Changelog:

* Removed libsanta-specific code, since [there is a package for it](https://bitbucket.org/haikuports/haikuports/src/c22362297cc83ccb3647eba1186f1055a8edf521/haiku-libs/libsanta).