[Rd] For integer vectors, `as(x, "numeric")` has no effect.

[Benjamin Tyner]

Perhaps it is not that surprising, given that

     > mode(1L)
     [1] "numeric"

and

     > is.numeric(1L)
     [1] TRUE

On the other hand, this is curious, to say the least:

     > is.double(as(1L, "double"))
     [1] FALSE

> Here's the surprising behavior:
>
>     x <- 1L
>     xx <- as(x, "numeric")
>     class(xx)
>     ## [1] "integer"
>
> It occurs because the call to `as(x, "numeric")` dispatches the coerce
> S4 method for the signature `c("integer", "numeric")`, whose body is
> copied in below.
>
>      function (from, to = "numeric", strict = TRUE)
>      if (strict) {
>          class(from) <- "numeric"
>          from
>      } else from
>
> This in turn does nothing, even when strict=TRUE, because that
> assignment to class "numeric" has no effect:
>
>      x <- 10L
>      class(x) <- "numeric"
>      class(x)
>      [1] "integer"
>
> Is this the desired behavior for `as(x, "numeric")`?