Whitelist blacklisting pcntl_ functions for setup checks so Debian installs don't fatal instantly
Summary: See IRC. This is dumb but I think we should try to work by default on Debian, and it doesn't cost us too much. See inline comment for more.
Test Plan:
- No `disable_functions`, restarted, worked fine.
- Set `disable_functions = pcntl_derp`, restarted, worked fine.
- Set `disable_functions = derp`, restarted, setup fatal.
Reviewers: btrahan
Reviewed By: btrahan
CC: aran
Differential Revision: https://secure.phabricator.com/D6741