bug#29108: 25.3; ERC SASL support

[Ulrich Mueller]

ERC is a little behind the times by not supporting SASL, so please
pretty please can we have this?

Not sure if it helps, but archive.org has a partial copy of the original
git repository:
https://web.archive.org/web/20180611034438if_/https://github.com/jane-lx/erc-sasl

Most importantly, it does have erc-sasl.el which AFAICS is the only
relevant file.

There also is a fork of the repository on Github:
https://github.com/suhailshergill/erc-sasl

Apparently it has no additional commits beyond the original repository
and erc-sasl.el is identical to the one found at archive.org.

Looking at commit history, there are 4 commits in 2012 (all by
Joseph Gay). Their parent is commit 9497cc9 which is also the tip of the
ERC repository at https://git.savannah.gnu.org/cgit/erc.git.

Would this be enough for inclusion in Emacs, given that erc-sasl.el has
a GPL license notice and that copyright papers for the author are on
file (or at least message #13 says so)?