t3lib_div::readLLXMLfile does not use localized content anymore
In bug #17894 the localization of other languages (besides the 'default' language) should be move to an external file to prevent loading unused string data.
If this file generated by t3lib_div::llXmlAutoFileName doesn't exist, the localized part is set to an empty array at the end of t3lib_div::readLLXMLfile.
The solution is to check whether this external file exists.
Affects TYPO3 4.1.4 and Trunk when locallang.xml files of extensions were modified locally or extension were updated from TER and have a modified locallang.xml.
(issue imported from #M6924)