[SECURITY] Fix RCE in swiftmailer

A remote code execution vulnerability was fixed upstream
which is now also fixed in the code we deliver with TYPO3.

This is not a full upgrade of the library but a backport
of the security fix.

Change-Id: I9bc6839c61724e9af43c9bfed68fb9d608646e30
Resolves: #59573
Releases: 4.5, 4.6, 4.7, 6.0, 6.1, 6.2
Security-Commit: d4119b872c8cd80782ef25a36fdd7a88b2bdac1c
Security-Bulletin: TYPO3-CORE-SA-2014-002
Reviewed-on: http://review.typo3.org/33452
Reviewed-by: Oliver Hader <oliver.hader@typo3.org>
Tested-by: Oliver Hader <oliver.hader@typo3.org>