Handle opcache_invalidate() being disabled on shared hosting platforms
Handle opcache_invalidate() being disabled on shared hosting platforms

This fix makes twig gracefully fail on opcache API being disabled on shared hosting platforms for security reasons.
Tested with Grav CMS.
twigphp/Twig,nicolas-grekas/Twig,nicolas-grekas/Twig,nicolas-grekas/Twig,twigphp/Twig,nicolas-grekas/Twig,twigphp/Twig,nicolas-grekas/Twig