Breaking change in path normalizeString in node 9.9.0

[xPaw]

I believe #19237 to be the culprit of this change.

I believe that PR unintentionally changed the behaviour of at least path.resolve which was not documented in the changelog.

We have a specific test around path.resolve and it started failing after 9.9.0 was released. See https://travis-ci.org/thelounge/thelounge/jobs/356475798#L582

https://github.com/thelounge/thelounge/blob/844ca1fbe602aa291b54085a6cf69198ea4a5390/test/src/helperTest.js#L14-L16

On 9.8.0 this happens:

> require("path").resolve("a\\b")
'/home/xpaw/a\\b'

But on 9.9.0 it seems that separator is changed to the OS specific one.

> require("path").resolve("a\\b")
'/home/xpaw/a/b'

[targos]

I have a fix ready. Just need to write tests.

[targos]

#19520