Clipping warning option

[Andrusian]

We REALLY need a clipping warning or error flag. It would stop the script on sustained clipping so you can fix it.

Now, this check will burn a lot of time, so this could be a line you enter into the script during development and then turn off once you are done. There are only a few spots where it is possible to do this - mix command is one. I tried adding the code just before the final signal is copied but it is WAY too slow. This will visually complicate the code even further, so we have to be careful on this.