* NEW: Support for the new USE instruction.

[COMPILER]
* NEW: A class header now can include USE "xxxx" declarations, where "xxxx"
  is a component name. It means that the specified component will be loaded
  when the class is initialized, the first time it is loaded.


git-svn-id: svn://localhost/gambas/trunk@6648 867c0c6c-44f3-4631-809d-bfa615b0a4ec