Don't count "\r" or "\n" for purposes of linewrapping text in Differential

Summary: This should all go away at some point when we move to fluid layout, but don't be more annoying than necessary in the meantime.

Test Plan: Meta.

Reviewers: vrana, btrahan

Reviewed By: vrana

CC: aran

Differential Revision: https://secure.phabricator.com/D3788