facebook/hhvm — pull request #4281 by icambridge (2014-11-18 20:09:20+00:00)
Title: Add PREG predefined constants

I've added the predefined preg constants as defined on http://docs.hhvm.com/manual/en/pcre.constants.php.

I looked at `hphp/hack/hhi/constants.hhi` which defined constants as zero. So I followed that.