[TASK] Drop type=select neg_foreign_table

Drop the functionality to store relations to a second table
in type=select fields as negative uid values.

Resolves: #69028
Releases: master
Change-Id: Ifa4fab62ea01f4aae3647802a22518792f70f350
Reviewed-on: http://review.typo3.org/42597


Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Frank Nägler <frank.naegler@typo3.org>
Tested-by: Frank Nägler <frank.naegler@typo3.org>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>