[#34028] Fixed PHPMailer with attachment(s)

I found the PHPMailer deployed (v5.2.6) unable to send mail with attachments (PDF in my case). Despite the correct settings (var_dumped the mailer object before calling `Send()`) i always receive empty emails (no body despite a body was set) and no attachment.
After several hours of playing around and breaking my head i decided to checkout the latest PHPMailer from github and try to send mail directly (without the use of JMail). And it worked right out of the box. Everything arrived as intended.

Since PHPMailer evolved (its v5.2.8 now) several slight changes where applied. Those relevant for Joomla! were part of my refactoring. In fact these changes are only case changes of the method names to call from PHPMailer and adding two more imports to the head of JMail. With these changes sending mail with and without attachments works properly (at least for me).

But i suppose the automated tests require some changes regarding the method name case changes.
Here is a bug.
you allways remove the first attachment (id = 0).

'if (isset($this->attachment[0]))'
should be
'if (isset($this->attachment[$index]))'