feat: Node v6.10 API compatibility

[SpainTrain]

BREAKING CHANGE: This is a complete rewrite based upon the actual node source code and tests.

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This change is 

[pcgilday]

Reviewed 14 of 22 files at r1, 8 of 8 files at r2.
Review status: all files reviewed at latest revision, 3 unresolved discussions, some commit checks failed.

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a discussion (no related file):
I think it looks good, been a while since I've reviewed some of this syntax though haha 😄

Once builds are passing I'll give a final look and squirrel.

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src/index.js, line 90 at r2 (raw file):

  var n, m, hexchar, c;

  for (var inIndex = 0, outIndex = 0; ; inIndex++) {

I've always preferred the format ++inIndex, which is used below. Either way I would suggest to stick to one.

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src/index.js, line 222 at r2 (raw file):

      continue;
    }
    // Surrogate pair

BTW - TIL what a surrogate pair was 🙃

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Comments from Reviewable

[SpainTrain]

Reviewed 16 of 22 files at r1.
Review status: 19 of 22 files reviewed at latest revision, 2 unresolved discussions.

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src/index.js, line 90 at r2 (raw file):

Previously, pcgilday (Patrick Gilday) wrote…

I've always preferred the format ++inIndex, which is used below. Either way I would suggest to stick to one.

as indicated in the comment at the top of this file, this is copied from node source https://github.com/nodejs/node/blob/v6.10.2/lib/querystring.js

plus this isn't just a matter of style/taste, prefix is a different operation than postfix https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Arithmetic_Operators#Increment_()

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Comments from Reviewable

[SpainTrain]

Reviewed 2 of 22 files at r1, 6 of 8 files at r2, 1 of 3 files at r3, 2 of 2 files at r4.
Review status: all files reviewed at latest revision, 2 unresolved discussions, some commit checks failed.

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Comments from Reviewable