[BUGFIX] PHP filesystem functions are locale dependent

PHP filesystem functions like pathinfo, dirname and
basename are dependent on the locale set in PHP.
If one enables UTF8filesystem in the install tool, he may
use non-ascii characters in filenames and directory names.
For this to work properly you need to configure
SystemLocale, too.

The file abstraction layer classes need to take care of
the SystemLocale; to avoid code duplication new static
wrapper functions have been introduced.

Change-Id: I635e18d7ed08d928c6c4e427c0348dd46d9c5900
Releases: 6.0, 6.1
Resolves: #45982
Reviewed-on: https://review.typo3.org/19444
Reviewed-by: Anja Leichsenring
Tested-by: Anja Leichsenring
Reviewed-by: Oliver Hader
Tested-by: Oliver Hader