Treat @meth annotation as making the type uncurried.

[cristianoc]

This restores examples in the documentation that have been broken since compiler version 9.0:

type person = {@meth "say": (string, string) => unit}

@val external john: person = "john"

john["say"]("hey", "jude")

Since there's no way in the .res syntax to call methods, the @meth annotation simply makes the type uncurried.

So in practice it's just redundant and can be removed in future.