Merge: 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

Pull-Request: #1048
Reviewed-by: Alexandre Terrasa <alexandre@moz-code.org>
Reviewed-by: Lucas Bajolet <r4pass@hotmail.com>

diff --cc src/parser/parser.nit
Simple merge

diff --cc src/parser/parser_abs.nit
Simple merge

diff --cc src/parser/parser_nodes.nit
Simple merge

diff --cc src/parser/parser_prod.nit
Simple merge