[TASK] Update the comment of stdWrap_char to include ASCII limitation

The PHP char() function only works reliably with ASCII codes
independent of the actual char set.

See http://php.net/manual/en/function.chr.php

Releases: master
Resolves: #76315
Change-Id: Ia87b95239fc4678f297571704f031003f84a5759
Reviewed-on: https://review.typo3.org/48306


Reviewed-by: Morton Jonuschat <m.jonuschat@mojocode.de>
Tested-by: Morton Jonuschat <m.jonuschat@mojocode.de>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>