Improve IPv6 support

[Achilleshiel]

This improves the handling of hosts.

This makes the following types of host a valid options:

• [::1]
• ::1
• 192.168.100.1
• 192.168.100.1:123
• [::1]:8080
• example.com
• example.com:8080

Closes #313

[aler9]

Hello, for maintainability reasons my approach is to produce code that is as similar as possible to the standard library. I took a look at net/http, and conversion between URLs and addresses is performed by this single function:

https://cs.opensource.google/go/go/+/refs/tags/go1.20.5:src/net/http/transport.go;l=2747

This was adapted for RTSP and merged in #316. It doesn't support all the host types you listed, in particular, it turned out that this kind of addresses:

http://::1/path

Is not supported by net/http, therefore there's no reason to support it here.

Thanks for providing this contribution that allowed to develop the final patch.

[Achilleshiel]

it turned out that this kind of addresses:

http://::1/path

Is not supported by net/http, therefore there's no reason to support it here.

That's correct, as that is not a valid url :). But ::1 is a valid hostname outside of an url.