Trubostat: Refactor delta functions

- merge delta_cpu in for_all_cpus_delta
- for_all_cpus_delta: don't resolve pointers that are not used
- add comments
Turbostat: Re-order code and add comments

No algorithmic change in this commit
Turbostat: Fix minor compilation warnings
Turbostat: Refactor topology probing

Only probe the topology once and store in locally
Turbostat: last re-ordering of the module
Turbostat: this code can fail in fact...
Turbostat: fix allocate_cpu_set
Turbostat: fix topology detection