Kotlin Maps with non-string non-numeric keys should map to Map instead of an Object

[brezinajn]

Kotlin Maps using keys other than number and string should map to Map instead of object.

data class Foo(val map: Map<Key, String>)

maps to

interface Foo{
    map: { [key: Key]: string };
}

which is invalid. It should map to

interface Foo{
    map: Map<Key, string>
}