Real-time error checking issues with custom namespaces

Hi!

The compiler didn't work correctly in these cases:

Case 1:

Wrong code:
```as
EventPriority.origin::HIGHEST
```
Correct code:
```as
EventPriority.hidden::HIGHEST
```

There's no `HIGHEST` property under the `origin` public namespace. But there's no error displayed.

Case 2:

Wrong code:
```as
override origin function x(value:Number):void
{
super.origin::x = value;
}
```
Correct code:
```as
override origin function set x(value:Number):void
{
super.origin::x = value;
}
```

Missing `set` but there's no error displayed.

These errors still occurred when I compiled my app/lib. But it would be better if I can see them sooner.

Thanks!