Allow TypeName multinames to contain forward references

Related: https://github.com/mozilla/shumway/issues/1110

With this patch, the [FlashCC Hello World](https://gist.github.com/adammw/c1cb328956ff41fbdd0b) abc file, [download here](https://gist.github.com/adammw/c1cb328956ff41fbdd0b/raw/1edfd6eeb4a642a7c65ff53143cdb8405895d4eb/hello.abc), now is parsed correctly.