Add support for certfp

[Tyil]

I can't seem to find any pointers in documentation or source for IRC::Client to make use of certfp. I would like to see support for this in the module, as I want to make use of this for one of my bots.

[zoffixznet]

It's possible :ssl and :ca-file options provide the means to use that service already. Looks like when they were added no documentation was created for how to actually use those options.

[Tyil]

Ah, I did not think ca-file would stand for that. I had assumed it ment the certificate of the CA of the certificate provided by the server. I'll try to use :ca-file when I get home.

Thanks for the quick response :)

[Tyil]

I tried to supply a certificate with :ca-file, but I'm getting the error "Certificate contains no altnames to check host against". I found this error message using the patch from #60.

[Tyil]

Okay, that specific error seems to have come from a faulty certificate. It did connect to another server, but it does not show a certificate fingerprint to associate with certfp when a :ca-file is passed.