Refactors _deepEqual and fixes a few code paths that lead to
behaviors contradicting what the doc says. Before this commit
certain types of objects (Buffers, Dates, etc.) are not checked
properly, and can get away with different prototypes AND different
enumerable owned properties because _deepEqual would jump to
premature conclusion for them.

Since we no longer follow CommonJS unit testing spec,
the checks for primitives and object prototypes are moved
forward for faster failure.

Improve regexp and float* array checks:

* Don't compare lastIndex of regexps, because they are not
  enumerable, so according to the docs they should not be compared
* Compare flags of regexps instead of separate properties
* Use built-in tags to test for float* arrays instead of using
  instanceof

Use full link to the archived GitHub repository.

Use util.objectToString for future improvements to that function
that makes sure the call won't be tampered with.

PR-URL: #11128
Refs: #10282 (comment)
Refs: #10258 (comment)
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>

Use the term "Abstract Equality Comparison" and "Strict Equality
Comparison" from ECMAScript specification to refer to the operations
done by `==` and `===`, instead of "equal comparison operator" and
"strict equality operator".

Clarify that deep strict comparisons checks `[[Prototype]]`
property, instead of the vague "object prototypes".

Suggest using `Object.is()` to avoid the caveats of +0, -0 and NaN.

Add a MDN link explaining what enumerable "own" properties are.

PR-URL: #11128
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>