[Powertop] Completion of error handling

Hello, I have looked at a few source files for your current software. I have noticed that some checks for return codes are missing. Would you like to add more error handling for return values from functions like the following? - fputs ⇒ finish_report_output https://github.com/fenrus75/powertop/blob/79123b34cf2cac2edeb918087dfc73f... - pthread_create ⇒ cpu_calibration https://github.com/fenrus75/powertop/blob/cdff23d6e40e31a68286a51e3c94c8a... - pthread_join ⇒ extech_power_meter::end_measurement https://github.com/fenrus75/powertop/blob/a5465a282107da5205b7928fe4ce4f6... Regards, Markus