Chained CPU determination lookup

[PragTob]

There's a lot of discussion of this topic in #108 . It's not a high priority now but I wanted to log the issue :) Oh yeah, this concerns Linux for now.

Basically, we got lots of different places where depending on the system we might get better or worse information (or none at all). Atm we use proc/cpuinfo but that might be hard to parse/architecture dependent. /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq is pretty cool but normal users don't always have access. lscpu might also work.

An idea would be that we perform a chained lookup like try sys/... first and see if we find good enough information, otherwise try another method and so on...