Add licensing information/attribution

[lukasstadler]

it would be great if you could add licensing information, i.e., where the content in this repository is coming from, which licenses/attributions (BSD, MIT, etc.) it has, and what the license of the parts that are not coming from somewhere else is.
that would make it much easier to use, and will also expose problems like incompatible licenses, if there are any.

[pointhi]

Benchmarking-Harness

Based on https://github.com/nicopauss/C-Hayai which is based on https://github.com/nickbruun/hayai

License: zlib + additional beer clause

Benchmarks

License	Number of Projects
MIT	24
Apache 2.0	6
BSD-2-Clause	8
BSD-3-Clause	14
zlib	3
CC0	3
Unlicense	3

Other parts (our own stuff)

has to be decided, should be something compatible to all licenses stated above