GitLab

Add Darwin swap meter

(See #292.)

OpenBSD port updates and error exit improvements

err.h functions corrupts the terminal when using curses.

Fix a case where the usertime calculation can overflow (see issue #202)

Darwin cpu average

add hint about system configuration file

Closes #293.

PPID and JID update fix

Fixed reparenting issue. PPID should be updated each refresh as any process can get reparented to either
PID1 or even any other PID (if there are custom reapers in the system).
Similar issue with jails, elevated process can ask kernel to attach itself into any jail at any time,
thus JID and jail name can change each refresh cycle.

https://developer.apple.com/library/mac/documentation/Darwin/Reference/ManPages/man3/signal.3.html

Add OpenBSD signals

FreeBSD
Linux
Other platforms will have it undefined for now.

htop fails to compile with:

```text
SignalsPanel.c:32:49: error: use of undeclared identifier 'Platform_signals'
      Panel_set(this, i, (Object*) ListItem_new(Platform_signals[i].name, Platform_signals[i].number));
                                                ^
1 error generated.
*** Error code 1
```

Implementations for Linux (tested) and FreeBSD (still untested, thanks to @etosan for providing the table).
Darwin and OpenBSD(ping @mmcco) builds should be broken now, pending their own tables.