HaxeContext#ResolveType(): fix error with toplevel import

The following would produce an error because the code didn't consider the possibility of a toplevel-import / an import without a dot.

```haxe
import Map;

abstract StringMapIterable<V>(Map<String,V>) from Map<String,V> {
        public function new(v:Map<String,V>) this = v;
        public function get() return this;
        static public function iterator<X>(i:StringMapIterable<X>) : StringMap.StringMapValueIterator<X> { return i.iterator(); }      
}
```