Improve PHP7 handling of include-time parser-like fatals like "class must implement all abstract methods"
Ref T12101. Although PHP7 raises parse errors as throwables, it still just instantly fatals for some types of parser-like error.
We currently silence these, so they can cause the process to appear to exit abruptly. Instead, unsilence them.
- Don't implement all abstract methods.
- Run arc unit.
- Before: silent fatal.
- After: useful error.
Reviewed By: amckinley
Maniphest Tasks: T12101
Differential Revision: https://secure.phabricator.com/D19001