Silence most E_STRICT errors

Bug 1268746: In PHP 5.4 E_ALL changed to include E_STRICT, causing Mahara to throw
a lot of strict standards errors. This should silence most of them.

HOWEVER, because most strict standards happen at compile-time, this will have no
effect on strict standards errors caused in the files that have already been
loaded by the time we call error_reporting() and set_error_handler(), which includes:
 - The file invoked directly by the URL
 - init.php
 - errors.php
 - config.php
 - config-defaults.php

Change-Id: I7a7fdf7facb1f30e186a0e8a27f1c3b7473200da