[5.6] Changed '/' to DIRECTORY_SEPARATOR

[TBlindaruk]

No description provided.

[carusogabriel]

Maybe is something we can do everywhere, as Laravel is use in different environments 🤔

[antonkomarev]

@carusogabriel windows eats both of slashes as valid ones and Unix strictly uses /.
This comment is not against this commit. It's just about thing that nothing will be changed by this commit.

[TBlindaruk]

@a-komarev ,

I have found an issue #8913
And fix it: #8916

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Also, we have o lot of PR already related to DIRECTORY_SEPARATOR
https://github.com/laravel/framework/pulls?utf8=%E2%9C%93&q=is%3Apr+is%3Aclosed+DIRECTORY_SEPARATOR

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Also we have a lot of DIRECTORY_SEPARATOR constants in Foundation/Application.php.
I think will be better to have a one code style (at list in one file)

[antonkomarev]

@TBlindaruk I'm totally agree that consistency is a key for a good software. Glad you've linked issues to this PR. That gives more weight to it.