Merge pull request #937 from leobalter/yield-star

src/async-generators/yield-star-async-next.case

src/async-generators/yield-star-async-return.case

src/async-generators/yield-star-async-throw.case

src/async-generators/yield-star-sync-next.case

src/async-generators/yield-star-sync-return.case

src/async-generators/yield-star-sync-throw.case

...xpressions/async-generator/named-yield-star-async-next.js

...ressions/async-generator/named-yield-star-async-return.js

...pressions/async-generator/named-yield-star-async-throw.js

...expressions/async-generator/named-yield-star-sync-next.js

...pressions/async-generator/named-yield-star-sync-return.js

...xpressions/async-generator/named-yield-star-sync-throw.js

...uage/expressions/async-generator/yield-star-async-next.js

...ge/expressions/async-generator/yield-star-async-return.js

...age/expressions/async-generator/yield-star-async-throw.js

...guage/expressions/async-generator/yield-star-sync-next.js

...age/expressions/async-generator/yield-star-sync-return.js

...uage/expressions/async-generator/yield-star-sync-throw.js

...ns/class/async-gen-method-static-yield-star-async-next.js

.../class/async-gen-method-static-yield-star-async-return.js