Improve LINT_DOS_NEWLINE behavior
Summary: Improve the behavior of ArcanistTextLinter in dealing with LINT_DOS_NEWLINE. In particular, provide replacement text so that these linter issues can be autofixed.
Test Plan: Added a unit test.
Reviewers: Blessed Reviewers, epriestley
Reviewed By: Blessed Reviewers, epriestley
Subscribers: epriestley, Korvin
Differential Revision: https://secure.phabricator.com/D10472