Fix build warnings

[cosminpolifronie]

There were lots of build warnings on MacOS because of using lots of old dependencies.
All of them have been updated to the latest versions and removed from the repository.
All dependencies are now downloaded from GitHub, using the latest tags or commits at the time of writing.

The only remaining MacOS warning is given in AppleSSL, as SecureTransport has been deprecated since macOS 10.15.
I am not familiar with those TLS paths and there are no TLS tests in the library so I don't think I'm the right person to add a Network.framework implementation, even if AI would implement it.

I will leave that to someone who has an interest in using the newer Apple SSL framework.

[bsergean]

There are too many changes bundled into this.

Could you break it down into a few different ones, one of them being using cmake to fetch dependencies. The build is failing btw for some reason.

[cosminpolifronie]

The commits can be reviewed one by one, the changes are not big for each (they are quite small for a pull request each) and are exactly described in the commit messages.

I will take another look at the builds. It seems the GH builds you have apply much stricter warning flags and error on warning.

It would have been nice to have those included in the root CMakeLists.txt.

[cosminpolifronie]

I can see the builds were started before #571 was merged, which contained some mbedtls build system fixes. Could you please re-run the builds so I can focus on the actual issues introduced by this PR?

[cosminpolifronie]

It seems there were some manual changes done to msgpack11 that fixed the exact build failures we are seeing here.
I have pushed those changes upstream.
The builds should pass after the PR is merged upstream and IXWebSocket starts using it.
ar90n/msgpack11#19