Allow using phlog() without initialization

Summary:
We call it in places where PhutilErrorHandler::initialize() wasn't called, e.g. in cache used in unit tests.
We can call the init on other places but this seems better as I see no reason why it must be initialized.

Also use time format available on Windows.

Test Plan:

phlog('It works!');

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D5646