templates for yield star flow

Add cases for abrupt completions in yield* in async generator - next

Add async generator error templates for destructuring binding

Add async generator templates for destructing binding

Add escape-above-astral.js to cover escaping code units as encoded from extended unicode escape. (#942)

Closes #883

* Tests for throwing a TypeError in the TypedArray constructor on a detached buffer

Detached buffer causes an exception
- If it's already detached going into the constructor
- If the byteOffset coercion causes it to be detached

Tests are valid in ES2017

* Test that TypedArray constructor throws when detaching buffer in length calculation

This test is only valid with the PR in https://github.com/tc39/ecma262/pull/852

* Rename files per review

In https://github.com/tc39/ecma262/pull/853 , standard semantics
for this case are proposed. This patch tests the case.

The change is proposed in https://github.com/tc39/ecma262/pull/856
as a fix to https://github.com/tc39/ecma262/issues/855

Here, the ToNumber coercion is done only once, rather than on each
iteration. It does not appear that there were previously any
tests against repeated coercion for this parameter previously.

Tested this test against V8, which failed, as V8 implements the
current spec rather than the proposed one.

Add async-gen templates for params in the test gen tool

Add feature flags for tests on object rest spread

Add async generator templates

Fix case sensitive

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