[BUGFIX] starttime / endtime l10n_mode exclude in core tables

starttime/endtime can be set different in localisations
but are (usually) not respected. This patch modifies
the behaviour inside localisations to show a readonly
value of the original starttime/endtime-values.

Change-Id: If7e32b0c8a628698115c60ec570c2526e5bb3546
Resolves: #24211
Reviewed-on: http://review.typo3.org/3984
Reviewed-by: Tolleiv Nietsch
Tested-by: Tolleiv Nietsch
Reviewed-by: Björn Pedersen
Reviewed-by: Susanne Moog
Tested-by: Susanne Moog