Like primarySlavePortNumber in currentDS

Preliminary work to build ppsi as object files of wrc
instead of building an intermediate archive.
This simplifies the definition of flags.

Also adjust some include directives

Avoid uninitialized wrh servo

The read_calibration_data functions still exist but do not
return anymore the clock period.

Mainly refactoring.

It is just setting the clock_period

and replace it by an assert