[CLEANUP] Deprecate DataHandler property stripslashes_values

The functionality is unnecessary and it's confusing when using
DataHandler that it must be explicitly set to FALSE to handle properly
prepared data. The only place in the core where it was set to TRUE only
handles integer values.

Releases: master
Resolves: #65381
Change-Id: I968fccc9311bb9ad5f9153217ecf84ff4777df4a
Reviewed-on: http://review.typo3.org/37316


Reviewed-by: Benjamin Mack <benni@typo3.org>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>