The change is done in the following patch, where default options
have a null prototype. This matches what other Intl objects have.
https://github.com/tc39/proposal-intl-plural-rules/commit/1abe8af440fb47d888ace701e8a46559bdbe7b06

As per https://github.com/tc39/ecma402/pull/160 the formatToParts.length is set to 1.

Tests for ECMA 402 PR https://github.com/tc39/ecma402/pull/170
The tests on Date/DateTimeFormat are valid without the PR.

This proposal was started in https://github.com/tc39/ecma402/issues/122,
and specified in https://github.com/tc39/ecma402/pull/148

Tests doesn't use async functionality and don't call $DONE, so remove
"async" flag:
- src/params/error/async-gen-named-func-expr.template
- test/language/expressions/async-generator/params-named-dflt-abrupt.js
- test/language/expressions/async-generator/params-named-dflt-ref-later.js
- test/language/expressions/async-generator/params-named-dflt-ref-self.js

Intl.PluralRules.prototype is no longer a Intl.Prototype instance:
- test/intl402/PluralRules/prototype/prototype.js

Intl.PluralRules throws an error when called as a function:
- test/intl402/PluralRules/undefined-newtarget-throws.js

Module namespace objects call OrdinaryDelete for symbol properties:
- test/language/module-code/namespace/internals/delete-non-exported.js

Async generators no longer retrieves "done" property twice:
- src/async-generators/yield-star-async-next.case
- src/async-generators/yield-star-async-return.case
- src/async-generators/yield-star-async-throw.case

Minor units of CLF is 4, so we need to test with maximumFractionDigits=3
to get an error:
- test/intl402/NumberFormat/dft-currency-mnfd-range-check-mxfd.js

DateTimeFormat.prototype.formatToParts length property was changed from
0 to 1:
- test/intl402/DateTimeFormat/prototype/formatToParts/length.js

minimumSignificantDigits and maximumSignificantDigits properties are
only retrieved once:
- test/intl402/NumberFormat/11.1.1_32.js

Closes #888

These tests are regression tests for V8 failures at top of tree,
https://bugs.chromium.org/p/v8/issues/detail?id=6015
https://bugs.chromium.org/p/v8/issues/detail?id=6016

Neither issue is present in JSC or SpiderMonkey. They are fixed
by the V8 patch
https://codereview.chromium.org/2717613005

Ref #856
Ref #857
Ref tc39/ecma402#128

1) (123.44500) == 123.444999999999993179
2) (123.44500).toPrecision(5) === "123.44" gives correct value in Chrome and Firefox;

Ref https://github.com/tc39/ecma402/issues/128

Note:
12344501000000000487815444678311936 === 12344501000000000000000000000000000 for binary64 floating points;

Ref https://github.com/tc39/ecma402/issues/128