Change docblocks to reflect magic static methods

Some IDEs use a class' @method docblock annotations to autocomplete, suggest and typehint magic methods for users. The `validator.php` class has these, but doesn't mark them as static, so the suggested `V::method()` syntax continuously throws errors:

![phpstorm](https://cloud.githubusercontent.com/assets/1274731/3169127/2c49ff2a-eb94-11e3-9749-27071a8f4170.png)

IDE I'm using is PHPStorm.

It appears that adding `static` annotations doesn't affect normal (dynamic) calls because PHP is okay with calling statics normally. Clearly the other way around doesn't seem to work!

(I noticed a similar request from long ago - I apologize if there's already a rationale for not doing this.)