[Twig] Allow usage of new Twig 2.0 function in Extension parser

[Haehnchen]

Twig_Function, Twig_Filter, Twig_Test were added in favoir of *Simple* ones

[Haehnchen]

see https://github.com/twigphp/Twig/blob/2.x/lib/Twig/Extension/Core.php

[stof]

I suggest also adding support for the new namespaced class names (which are aliases for existing Twig_* classes), which will make the code ready for Twig 3 (where only namespaced names will be kept AFAIK).

Symfony switched to namespaced names when referencing Twig classes.

[Haehnchen]

thx for this note. also easy. found some clear namespaces:

\Twig\TwigFilter
\Twig\TwigFunction
\Twig\TwigTest

[Haehnchen]

so done