Locally disable warnings

The new annotation `no_warning`, used in module, will disable specific (or all) warnings in the module.

~~~
module lexer is no_warning("missing-doc")
module parser is no_warning("missing-doc", "unread-variable")
module toto is no_warning("all")
~~~

Note: Now there is less noise, a future PR (currently in writing) will remove a lot of warnings in the `src/` directory.

Close #774