This will enable building the project using GNU Autotools without the need
to run in 'foreign' mode. This is done to maximize portability and simplify
packaging.

* `AUTHORS`: already covered by `git log` but easy to maintain -> added
* `COPYING`: already covered by `LICENSE` -> symlinked for compatibility
* `ChangeLog`: already covered by `git log` -> added explanation
* `README`: already covered by `README.md` -> symlinked for compatibility
* `NEWS`: already covered by `CHANGELOG.md` -> symlinked for compatibility

Note: For release tarballs, `ChangeLog` could be generated from `git log`
to make releases self-contained.