Implement Slices - struct elements only

[GraphR00t]

Inox slices are equivalent to Go slices. They are the primary way to create a sequence containing instances of a struct type.
Slices are not serializable.

struct Token {
    kind int
    start int
    end int
}

# allocate and initialize a slice of length 3 on the module's heap
tokens = [:]Token{{0, 3, 4}}

# allocate a slice on the module's heap
tokens = new([:]Token, 10)

# append a token at the end of the slice, should it work like Golang's append ?
tokens = appendto(tokens, Token{0, 3, 4})

# equivalent
appendto(&tokens, Token{0, 3, 4})