Unifies copyright statement across project

According to commit [a0368e7](https://github.com/clibs/clib/commit/a0368e730bda632a86e55b4e8873146baaad49ba), the project is copyright to `clib authors` - but in the files, it is copyright to @stephenmathieson. This pull request rights the various files in `src` to show the correct copyright statement, fixing the license.