New and improved? patch

[Dieter]

> 7.0 AMD64 # ./fwcontrol -f -5
> fwcontrol: main:set_root_node out of range: No such file or directory
> 
> "No such file or directory" seems wrong

err(EX_USAGE, "%s:set_root_node out of range", __func__);

Err() is correct for places where errno would be set, such as
checking the return code from read(2).  But for the range checks,
errno does not apply, so err() gives misleading results.

The err(3) man page isn't clear, but it looks like errx(3) is
the function you want for the range checks.

Changing err() to errx() gives:

7.0 AMD64 # ./fwcontrol -f 70
fwcontrol: main:set_root_node out of range