Summary: Some versions of PHP aren't very happy about both interfaces and superclasses defining a method. Just remove it from MentionableInterface and leave it as implicit.
Auditors: btrahan
Summary: Fixes T4036. Now if you say something on diff X like "This reminds me of Tx and Dy and commitHashFoo and Px." each of those objects gets a little visible transaction that the mention occurred. No feed, email, or notifications.
Test Plan: made a comment like above and verified transactions. also submitted a diff that "Fixes Tx" and Tx did not get the transaction as expected.
Reviewers: epriestley
Reviewed By: epriestley
Subscribers: joshuaspence, epriestley, Korvin
Maniphest Tasks: T4036
Differential Revision: https://secure.phabricator.com/D10451
