Check ELIST compatibility and functionality

[rscs]

From @KoraggKnightWolf in #bahamut: [16:54:06] <Koragg> I noticed in RPL_ISUPPORT that the ELIST tokens are in lowercase, though normally they are in uppercase, what was the reason to make the tokens themselves lowercase?

I don't think the case matters since the RFC (https://tools.ietf.org/html/draft-hardy-irc-isupport-00#page-11) says, "The following extensions, which a client MUST treat as being case insensitive are defined."

However, I will argue that we claim to support CMNTU when really we only support C and T. We sorta support U, M, and N as well, but not in the tokenized way required by the RFC.

So we should either fix ELIST to only include the tokens we support officially per the RFC, or add support for the tokens as defined in the RFC.