[Termtools] New benchmarks

Dear all,

new benchmarks are

- SRS encodings of variants of the Collatz conjecture by Yolcu, https://arxiv.org/abs/2105.14697. No tool could solve.

- Three minimalistic TRSs by Etienne Payet. Only NTI could show nontermination, very interesting!

- A TRS encoding of the Collatz conjecture using binary arithmetic by me (motivated by Larry Paulson, independent with the Yolcu's). No tool could solve.

You can view them by filtering benchmarks e.g. by "_21/".

https://termcomp.github.io/Y2021/job_47877_47875.html?filter0=_21/ https://termcomp.github.io/Y2021/job_47878_47876.html?filter0=_21/

Best, Akihisa