fixed some simple bug in variant.dt

[porky11]

namespace was forgotten,

[porky11]

I also added, that the main struct will be declared before the sub-structs are declared, so it's possible to do something like this:

(def-variant List ((Cons ((a (p List)) (b (p List))))
                    Null))

Following is still not possible, (and won't be, since it would result in a infinite struct):

(def-variant List ((Cons ((a List) (b List)))
                    Null))

[tomhrr]

Thanks, looks good.