Fix E_STRICT (strict standards) notifications

The Mahara codebase has a lot of older code that throws a lot of E_STRICT errors, if error reporting is set to include them. PHP best-practice is to fix these, so we should do that when the opportunity arises.

This has become more urgent now that PHP 5.4 includes "E_STRICT" in "E_ALL". Mahara 1.9 now includes a patch that sets error reporting to "E_ALL & ~E_STRICT" which will silence most E_STRICT notices. In order to find them for testing, you'll need to add this to your config.php:

$cfg->error_reporting = E_ALL | E_STRICT;