[BUGFIX] Fatal error on clearing all caches in backend

Due to a misconfiguration of a hook in EXT:lang, clearing all caches fails.
class.tx_lang_clearallcache.php -> class.tx_lang_clearcache.php

Change-Id: Ifebbc919cedb3bf04777772015e59c6eb2d908dd
Fixes: #32658
Reviewed-on: http://review.typo3.org/7357
Reviewed-by: Oliver Hader
Tested-by: Oliver Hader