Backport Ruby 2.4 support for Windows to 1.7.x

[nurse]

for master see #1618

[flavorjones]

Hi @nurse, thank you for this pull request. The next release of Nokogiri is intended to be 1.8.0, which would add Windows Ruby 2.4 support and remove Windows Ruby 2.1 support (which just reached EOL).

I was not planning on backporting Ruby 2.4 into 1.7.x, primarily because that's a lot of rubies to have vendored into the fat binary gem. I'm open to changing my mind, though.

Does anyone else feel strongly that we should cut a 1.7.x release adding Windows Ruby 2.4 support?

[larskanis]

IMHO we should release 1.8.0 ASAP - not another 1.7.x. Maybe with a prerelease first, but I wouldn't stick on the 1.7.x branch. I would also offer my help in bringing 1.8.0 out. @flavorjones What are the open tasks?

There are 2 remaining issues targeted to 1.8.0 on the current milestones list (the memory leak and the segfault). Both are present since years, so I wouldn't delay the 1.8.0 release by these two.

Nevertheless I see the urgent need to release a new fat binary gem for Windows, because I released RubyInstaller-2.4 last week. Although it's relatively simple to use the source gem instead, almost everyone stumbles into the issue #1618 first, and that isn't a nice welcome.

[flavorjones]

@larskanis thanks for replying. let's give @nurse the opportunity to respond.

Also - @nurse - if you'll kindly rebase onto v1.7.x, the concourse-ci check should pass (I've cherry-picked 9d24e8a onto v1.7.x).

[nurse]

@flavorjones I was OK to wait v1.8.0 (I created #1618) but I wait 3 months.
If v1.8.0 still requires more weeks, I want to release v1.7.3.

[flavorjones]

I commit to releasing 1.8.0 by this weekend. Will leave this open until then.

[nurse]

Sure, I wait it.

[flavorjones]

Closed, I've shipped 1.8.0 with Windows Ruby 2.4 support instead.