Display and link lint errors on line 0

Summary:
Some lint errors (e.g. Javelin) don't have a line number.
Put them on the first line.

Putting them above the first line would be even nicer but much more complicated.

Test Plan: Display diff with lint error on line 0 (D2583).

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Koolvin

Differential Revision: https://secure.phabricator.com/D2599