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events: add ability to prepend event listeners

Rodrigo Muino Tomonari requested to merge github/fork/jasnell/events-prepend into master

Pull Request check-list

  • Does make -j8 test (UNIX) or vcbuild test nosign (Windows) pass with this change (including linting)?
  • Is the commit message formatted according to [CONTRIBUTING.md][0]?
  • If this change fixes a bug (or a performance problem), is a regression test (or a benchmark) included?
  • Is a documentation update included (if this change modifies existing APIs, or introduces new ones)?

NOTE: these things are not required to open a PR and can be done afterwards / while the PR is open.

Affected core subsystem(s)

events

Description of change

A handful of modules (including readable-streams) make inappropriate use of the internal _events property. One such use is to prepend an event listener to the front of the array of listeners.

To address part of the issue, this adds a new optional bitwise flag to the addListener/on/once methods that, when set, causes the listener to be prepended.

Doc update and test case is included.

Fixes: https://github.com/nodejs/node/issues/1817

/cc @ChALkeR

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