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Keep scanning threads for versions before High Sierra 13.0.0 and after 13.3.0.

Based on: http://stackoverflow.com/questions/6788274/ios-mac-cpu-usage-for-thread
and       https://github.com/max-horvath/htop-osx/blob/e86692e869e30b0bc7264b3675d2a4014866ef46/ProcessList.c
This should be a fix for #361.

Works with:
- Darwin 9.8.0 (OS X 10.5.8) PPC
- Darwin 15.2.0 (OS X 10.11.2) Intel

err.h functions corrupts the terminal when using curses.

Change more fprintf(stderr, ...); exit(...); to err[x](...). Tweak a few existing ones and fix some style.