[BUGFIX] Make DataHandler aware of relations behind special=languages

The special TCA option "languages" makes some other TCA options like
foreign_table unnecessary which have been removed from
the sys_language_uid fields.

But DataHandler relies on the 'foreign_table' setting and therefore
needs some more information to resolve the related table
behind the "languages" option.

Resolves: #73182
Releases: master, 7.6
Change-Id: Id8f7f995d424f69fd5dce8e28cb1fc9db33fa0b0
Reviewed-on: https://review.typo3.org/46535


Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Daniel Goerz <ervaude@gmail.com>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Andreas Wolf <andreas.wolf@typo3.org>
Tested-by: Andreas Wolf <andreas.wolf@typo3.org>
Reviewed-by: Frank Naegler <frank.naegler@typo3.org>