...due to nested register_shutdown_handler() issue facebook/hhvm#2981.

Usage in Tester Environment::setupErrors().

Failing tests Runner.multiple-fails.phpt, resp. testcase-not-call-run.phptx.

Consenquences of this issue are (for HHVM only):

• fatal errors muted by shut-up operator aren't shown
• check for assertion count is not applied