Update PHPMailer to 5.2.9

Note this also update the symfony yaml component as this is just a composer update

Symfony YAML goes to 2.6.0. Main addition is this feature http://symfony.com/blog/new-in-symfony-2-6-support-for-object-maps-in-yaml-component

There is also a Joomla Filter package update (which when merged will fix the bug reported in #5013) which is also fully b/c

## Testing
You will need to test this on 3.4 alpha or directly on staging. If you test this on patchtester with Joomla 3.4 alpha you will need to manually add the ```composer.json``` file from the staging repo (https://github.com/joomla/joomla-cms/blob/staging/composer.json) or else you will get the error ```Error
The file marked for modification does not exist: composer.json``` as the composer.json file is not included in the distributed releases