limit thread usage to 'sane' default

[kosloot]

Most of the ticcltools provide a -t option to set the number of threads to run on.
It might be a good plan to check this number against the number of available processors and limit it to that number (or even 1 or 2 lower to leave some CPU to other processes).
Maybe we could introduce -t polite or -t max as a possibility? (machine independent)
@martinreynaert and @proycon do you have strong opinions about this?

[martinreynaert]

This is a sensible idea which warrants looking into in due time.

For now, I see quite a lot of more pressing matters with much higher priority in my schedule and project plannings.