[Twig] Finally resolve missing block completion in PhpStorm9

[Haehnchen]

If we are inside block tag no completion event is fired. also "hacked" SMART char-type workaround is not working.

Open external issue again. Old one: https://youtrack.jetbrains.com/issue/WI-24362

{% block <carpet+completion>  %}
{% endblock %}

[Haehnchen]

external:
https://youtrack.jetbrains.com/issue/WI-27021