Add abstract references support

https://github.com/zenparsing/es-abstract-refs

Symbol.referenceGet
Symbol.referenceSet
Symbol.referenceDelete
Function#@@referenceGet
Map#@@referenceGet
Map#@@referenceSet
Map#@@referenceDelete
WeakMap#@@referenceGet
WeakMap#@@referenceSet
WeakMap#@@referenceDelete

Dict.{...methods}[@@referenceGet]