Add two new functions to check if 'systemLocale'
setting is correct and if configured 'systemLocale'
supports UTF-8 when 'UTF8filesystem' is set.

Resolves: #55721
Releases: 6.2
Change-Id: Id9edfc896a87d5025a5170690a6b7d6eb25950e6
Reviewed-on: https://review.typo3.org/27510
Reviewed-by: Markus Klein
Reviewed-by: Tymoteusz Motylewski
Tested-by: Tymoteusz Motylewski
Reviewed-by: Jigal van Hemert
Tested-by: Jigal van Hemert