[TASK] Deprecate AbstractFunctionModule->incLocalLang()

Loading a locallang.xlf inside the abstract function module now uses the regular
$GLOBALS['LANG']->includeLLFile() of the current file, instead of doing a manual
check on .xml and .php extensions, which the LanguageService/LanguageFactory
is taking care of anyway.

The PHP method incLocalLang() and the now not necessarily needed $thisPath
are therefore marked as deprecated.

Resolves: #80511
Releases: master
Change-Id: I3a9d27bf794a4cd8c1f2d31ed9250d634aa68ee8
Reviewed-on: https://review.typo3.org/52209


Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>