Test suite: auto-catch perf regression
Arraymancer need a reliable way to automatically catch performance regression like these:
- https://github.com/mratsim/Arraymancer/issues/134
- https://github.com/mratsim/Arraymancer/issues/111

It should be based on a measure independent from the processor speed such as clock cycle.

One way to do it is via a bash script and using "perf". Note: perf can also measure branch mispredictions which can also be tested.

Another way is via the assembly instruction [RDTSC](https://fr.wikipedia.org/wiki/RDTSC)
Note: it might be necessary to set the processor affinity for RDTSC