GitLab

Move functions that read process data into LinuxProcess.c
and change flow from a monolithic `ProcessList_scan ->
ProcessList_goThroughEntries` into the following:

```
ProcessList_scan -> (Linux)ProcessList_goThroughEntries ->
ProcessList_scanProcess -> (Linux)Process_update
```

This will allow hooking plugins into the scanning
process.

Other platforms need to be similarly reworked.

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.