[BUGFIX] Prevent fatal error in stdWrap when compatibility6 is not loaded

When extracting compatibility6 it was forgotten to tackle stdWrap offsetWrap,
which uses a class of compatibility6.

We add a check for the extension and a deprecation notice to not use this
(really outdated) stdWrap anymore.

Resolves: #71704
Releases: master
Change-Id: I83d2ede014efd32a0241372df32f333d55f091ce
Reviewed-on: https://review.typo3.org/44805


Reviewed-by: Stefan Neufeind <typo3.neufeind@speedpartner.de>
Tested-by: Stefan Neufeind <typo3.neufeind@speedpartner.de>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>