Allow willLintPaths and didLintPaths to be overridden
Summary: I'm not sure if the upstream will be interested in this change, but we are writing a linter which works by running an external command on the entire repository. This can't be done with ArcanistExternalLinter at the moment, which meant that we ended up copy-pasting most of ArcanistFutureLinter. This would be a lot easier if we could override willLintPaths and didLintPaths, but these methods are currently marked as final. An alternative solution would be some sort of ArcanistLinter::transformPath method.
Test Plan: N/A
Reviewers: epriestley, Blessed Reviewers
Reviewed By: epriestley, Blessed Reviewers
Subscribers: faulconbridge, Korvin
Differential Revision: https://secure.phabricator.com/D19630