[CLEANUP] Remove old .xml and .php locallang references

There are still places in the CMS Core that reference locallang.php
and locallang.xml although the default is the XLIFF file format.

The old data from CSS Styled Content 6.1 and below are not respected
as they will be removed in a later patch anyway.

Resolves: #62828
Releases: master
Change-Id: Iff48c614627ad99a3c5c76e38dc595ac6d80063e
Reviewed-on: http://review.typo3.org/33949
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Benjamin Mack <benni@typo3.org>
Tested-by: Benjamin Mack <benni@typo3.org>