PTE should check if GD is installed

[maximejobin]

GD was not installed and no warning or error were raised to let the user know it needed the library.

I had to check the code and to find that out. A simple way to find that out:

<?php
if (extension_loaded('gd') && function_exists('gd_info')) {
    echo "GD library is installed.";
}
else {
    echo "GD library is NOT installed.";
}
?>

[sewpafly]

Thanks, I'll add this to the next version.