[TASK] Add XLF file checker for TRAVIS CI

The script checks for the presence of a t3:id in the XLF files.
Moreover the uniqueness is verified.

Resolves: #62965
Releases: master, 6.2
Change-Id: I8a2514b31c1484988ef7add937502424f64ed1e4
Reviewed-on: http://review.typo3.org/34229
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>