Change C binding variadic syntax to splats

[jhass]

From

lib X
  fun variadic(value : Int32, ...) : Int32
end

to

lib X
  fun variadic(*value : Int32) : Int32
end

Once #214 is implemented, the syntax for variadic callbacks should be

lib X
  type Callback = *Int32 -> Bool
end

The reasons are the same as always, replacing obsolete special cases with general constructs of the language.

[oprypin]

You might be confused here. The ... doesn't mean more arguments of the same type may follow, it means any number of any type of argument may follow.

[jhass]

How about

fun variadic(value : Int32, *args : *T)
alias Callback = Int32, *T -> Bool

then?

[asterite]

Syntax aside, there's no way to currently hold a pointer to a variadic/splat proc. The concept doesn't exist in the language, and I have no idea how it could be implemented.

The best thing to do is to use a regular Proc, make sure it's not a closure, and then cast it to Void* and pass that as the callback.