Link manual diff from lint error displayed at commit diff

Summary:
Some fields require displayed diff (e.g. Lines), some require last manual diff (Lint, Unit).
Lint requires both - it needs to find if the line with the error is displayed or not.

Test Plan: Displayed committed diff with lint errors, clicked on them, got last manual diff at the correct line.

Reviewers: epriestley, btrahan

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D3331