Add async-functions feature to more files (#1830)

...ements/class/async-meth-params-trailing-comma-multiple.js

...atements/class/async-meth-params-trailing-comma-single.js

.../statements/class/async-meth-static-dflt-params-abrupt.js

...ss/async-meth-static-dflt-params-arg-val-not-undefined.js

.../class/async-meth-static-dflt-params-arg-val-undefined.js

...atements/class/async-meth-static-dflt-params-ref-later.js

...atements/class/async-meth-static-dflt-params-ref-prior.js

...tatements/class/async-meth-static-dflt-params-ref-self.js

...nts/class/async-meth-static-dflt-params-trailing-comma.js

...class/async-meth-static-params-trailing-comma-multiple.js

...s/class/async-meth-static-params-trailing-comma-single.js

...atements/class/definition/class-method-returns-promise.js

...tements/class/definition/methods-async-super-call-body.js

...ements/class/definition/methods-async-super-call-param.js