Breaking: #92118 - TCA ctrl thumbnail setting dropped

See forge#92118

Description

The TCA setting $GLOBALS['TCA'][$aTableName]['ctrl']['thumbnail'] has been dropped.

Impact

Setting the control field for a custom table has no effect anymore.

Affected Installations

The setting has been used in the List module for tables with image fields to render a preview of attached images. It has been used for tt_content in core versions until TYPO3 v7. There are probably not many extensions using the setting. The List module will no longer show preview images for rendered rows.

Migration

Drop this setting during extension clean up. The setting is simply ignored, no PHP error will be thrown.