Small documentation corrections

[jwillikers]

This PR fixes small typos in the documentation and adds missing build dependencies necessary for building on Fedora.
This PR also adds the host option to the Mopidy configuration examples when using the TCP source.
Without host=127.0.0.1 I wasn't able to get the examples to work.

Some small improvements were made to the ALSA backend configuration examples.
The ALSA loopback device is now referred to by name instead of index since the index is subject to change.

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[kingosticks]

Surprised you need the host argument as the default is "localhost".

[jwillikers]

Surprised you need the host argument as the default is "localhost".

Me too, but apparently I'm not the only one: #511 (comment)
Does localhost use IPv6 instead of IPv4 in GStreamer or something?

[badaix]

Thanks!

[kingosticks]

Does localhost use IPv6 instead of IPv4 in GStreamer or something?

Sorry for the slow response. I don't think this is specific to GStreamer (which will surely be using the system resolver). Seems that on dual-stack systems, IPv6 is preferred over v4 and since localhost resolves to both 127.0.01 and ::1, the latter wins. I can see the same thing when I ping localhost on my machine.

Presumably listening/connecting on ::1 is fine providing that matches the other side. But if snapserver.conf is explicitly using 127.0.0.1 (as per the docs, does it even support hostnames?) then Mopidy using ::1isn't going to work. So I think this all makes sense and being explicit on both sides is the correct answer.

[badaix]

Just checked the code: the tcp stream doesn't do any host name resolution. Both, IPv4 and IPv6 should work, but no name resolution happens. I will create a feature request for this.

btw: on my Linux Mint machine I have localhost for IPv4 and ip6-localhost for IPv6:

 more /etc/hosts
127.0.0.1	localhost
127.0.1.1	Laptop

# The following lines are desirable for IPv6 capable hosts
::1     ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters

Now my IPs are publicly available in the internet, hope I will not get hacked.
It's Friday :)

[kingosticks]

btw: on my Linux Mint machine I have localhost for IPv4 and ip6-localhost for IPv6:

I have the same for my Ubuntu 20.04 machine. But my Fedora 33 and Raspbian systems have something more futuristic:

127.0.0.1       localhost
::1             localhost ip6-localhost ip6-loopback
ff02::1         ip6-allnodes
ff02::2         ip6-allrouters

I'm now going to turn my machines off to avoid the hacker onslaught.

[badaix]

First the hacker has to resolve the IP conflict between your and my IP addresses

[jwillikers]

Fedora 35:

127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain