Except stated otherwise in comment.

Fixes coding style. Formatting commits suck, incoherent coding style
sucks more.
https://suckless.org/coding_style/

this gives the compiler a chance to check weather the prototype and
definiton matches or not, which would catch issues like 3c47701.

If the connection is lost to the sndiod(8) daemon reset the
initialization to allow for a graceful restart.

- Edit compile instructions
- Reuse OpenBSD sndio implementation

Starting with OpenBSD 6.7 regular users cannot access raw audio devices
anymore, for improved security.

Instead use the sioctl_open(3) API to access and manipulate audio
controls exposed by sndiod(8). On the first call a permanent connection
is established with the running sndiod daemon, and call-back functions
are registered which are triggered when audio controls are changed
(e.g., a USB headset is attached) or when the volume is modified. On
subsequent calls we poll for changes; if there are no volume changes
this costs virtually nothing.

Joint work with Alexandre Ratchov

Based on functionality in dstat by Joerg Jung.

 - Remove <errno.h> because related functions are in util.c now
 - Remove corresponding <string.h> if not used otherwise

This is a first step to decouple formatting from information because of
two reasons:

 1. The components should only gather and return the values by design
 2. Fine grained user control should be a focus

Scaling will be implemented in a different way in a later commit.

Units should be added to the corresponding numbers