Improve PHP7 error reporting for include-time syntax errors
In PHP7, include_once may raise a Throwable which has a useless message and stack trace (neither point at the actual file or line where the error occurs).
Catch and mangle these so they're useful. This upgrades the message from syntax error: unexpected X so it has a file and line number.
Reviewed By: amckinley
Differential Revision: https://secure.phabricator.com/D18797