R1:c66954af262f

Fix a TODO

Summary: Rename `DifferentialChangesetParser::WHITESPACE_IGNORE_ALL` to `DifferentialChangesetParser::WHITESPACE_IGNORE_MOST`.

Test Plan: Browsed a diff with a few different settings for "Whitespace changes".

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: epriestley

Differential Revision: https://secure.phabricator.com/D11715