[WIP] Sync features with Node 9

[goto-bus-stop]

Still need to port:

• callbackify
• format
• inspect
• isDeepStrictEqual

[goto-bus-stop]

The new inspect() function is significantly bigger which is unfortunate. Hopefully common-shakeify can usually remove it from browser builds.

[goto-bus-stop]

Think I'll split this up so we can get promisify out the door first :P not that many people really need the new format features, probably!

[eemeli]

How could I help get at least the util.inspect part of this available on npm? I'd like to use it in eemeli/yaml-playground. Brief testing would suggest that it mostly works, except for indentation depth with Map and Set objects.

[BridgeAR]

What's the status here?

[BridgeAR]

Ping @goto-bus-stop

[goto-bus-stop]

promisify/callbackify was landed separately, debuglog is in another PR. Maybe we can extract the inspect progress from this as a separate PR too, but it may be tricky to reconcile the current master with this PR and with the latest Node.js implementation. No work happened here since the last visible changes.

I can't commit enough time to finish inspect in the near future

[ExE-Boss]

Node 10.12 and newer registers the util.inspect.custom symbol as nodejs.util.inspect.custom, making it possible to use Symbol.for('nodejs.util.inspect.custom') to get the equivalent util.inspect.custom symbol without depending on util:

Suggested change

	var customInspectSymbol = typeof Symbol !== 'undefined' ? Symbol('util.inspect.custom') : undefined;
	var customInspectSymbol = typeof Symbol !== 'undefined' && typeof Symbol.for !== 'undefined' ? Symbol.for('nodejs.util.inspect.custom') : undefined;

[ljharb]

Browsers, however, don’t register it, so I’d you don’t have util.inspect, there’s no point in having the symbol - why not just depend on util?

[ljharb]

Also, node 6.6-10.11 all require this code, and can’t rely on the shared symbol.