Update fortran90.html.markdown

[Ily83]

added DO CONCURRENT

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• [x] Pull request touches only one file (or a set of logically related files with similar changes made)
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[nbehrnd]

Thank you for the addition of this function introduced more recently to Fortran (in Fortran's time scale). For consistency of the format of presentation, may you please edit the comments into two-line comments, i.e., to substitute a)

! ISO Standard Fortran 2008 introduced the DO CONCURRENT construct to allow you to express loop-level parallelism

by

! ISO Standard Fortran 2008 introduced the DO CONCURRENT construct to allow you
! to express loop-level parallelism.

and b)

! Only calls to pure functions are allowed inside the loop and we can declare multiple indices:

by

! Only calls to pure functions are allowed inside the loop and we can declare
! multiple indices:

This is one of the convened rules to ease the eventual display as web page applying a one-for-all languages style sheet (though not always working for everyone's setup, e.g. example and example). Independent of the project, this restrain on the code blocks simultaneously eases to read your contributions here on GitHub's issue reports (no need for a horizontal scroll bar) and inspections of git's difference views in a terminal, too.

[Ily83]

Can I add more stuff here or should I need to do another pull request?

[nbehrnd]

Addition of @robochat (the initiator of the Fortran summary), addition of @mribeirodantas (one of those with the key to merge .and. more frequently seen).

[nbehrnd]

@Ily83 If the additional edit belongs to do concurrent, I suggest to amend the current PR. If it is independent, I would suggest a separate PR (as in atomic changes / one additional feature described at a time). If the edit requires do concurrent to be already described, I would file a PR after the current PR has been merged.