Fix failing unit test.

Summary: On PHP versions earlier than 5.4.0, \e is not a valid PHP escape character. Consequently, PhutilUTF8TestCase::testUTF8ConsoleStrlen will fail. Replace \e by its hexadecimal equivalent.

Test Plan: Ran unit tests.

Reviewers: hach-que, epriestley, Blessed Reviewers

Reviewed By: hach-que, epriestley, Blessed Reviewers

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D9615