Incompatibility with FreeBSD 13.0-RELEASE-p1

Hi ,

I think that i3status version : "i3status 2.13" is incompatible with FreeBSD 13.0-RELEASE-p1.

command used to check : `i3status -c ~/.config/i3status/config`

returns : `i3status: Memory status information is not supported on this system`

conf file :
```
# i3status configuration file.
# see "man i3status" for documentation.

# It is important that this file is edited as UTF-8.
# The following line should contain a sharp s:
# ß
# If the above line is not correctly displayed, fix your editor first!

general {
colors = true
interval = 5
}

order += "ipv4"
order += "wireless wlan0"
order += "ethernet _first_"
order += "battery all"
order += "disk /"
order += "load"
order += "cpu_temperature 0"
order += "memory"
order += "tztime local"

wireless wlan0 {
format_up = "W: (%quality at %essid) %ip"
format_down = "W: down"
format_quality = "%03d%s"
}

ethernet _first_ {
format_up = "E: %ip (%speed)"
format_down = "E: down"
}

battery all {
format = "%status %percentage %remaining"
}

disk "/" {
format = "%avail"
}

load {
format = "%1min"
}

memory {
#format = "%used | %available"
format = "%available"
threshold_degraded = "1G"
format_degraded = "MEMORY < %available"
}

tztime local {
format = "%Y-%m-%d %H:%M:%S"
}

cpu_temperature 0 {
path = "dev.cpu.0.temperature"
}
```

Regards !