Parser changes in Haxe 4

[Gama11]

A list to keep track of the Haxe 4 parser changes hxparser is missing:

• [ ] arrow functions
• [ ] final
• [ ] new function type syntax
• [ ] allow bool as const params
• [ ] enum abstract
• [ ] extern field
• [ ] @:a.b
• [ ] var ?x:Int
• [ ] Intersection Types