Improve `@Export` to support `Variant` and `GArray` types.

[EstevanBR]

If you try to @Export a GArray or a Variant you get this error:

GArray

if let res: GArray = args [0].asObject () {

instance method 'asObject' requires that 'GArray' conform to 'GodotObject'

In this case we'd want GArray(args[0])

Variant

if let res: Variant = args [0].asObject () {

instance method 'asObject' requires that 'Variant' conform to 'GodotObject'

In this case we could just have if let res = args.first (IMO we should be using args.first any place we use args[0])

[migueldeicaza]

Fascinating, in both cases, those are the incorrect casts.

There is no need of the asObject in the Variant case, and for the GArray case we need to call GArray (args[0]) instead.

[migueldeicaza]

Almost have this fixed.