[BUGFIX] Provide default value for field tt_content.filelink_sorting

Changing the field type for filelink_sorting to a text type that supports
a default value allows inserts into tt_content to succeed when no sorting
option was provided, fixing problems with MySQL strict mode.

Resolves: #67186
Resolves: #52206
Releases: master
Change-Id: Ie9a06fff14ec62c9cbc8d15cc957f5fcbe698393
Reviewed-on: http://review.typo3.org/41756


Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Daniel Goerz <ervaude@gmail.com>
Reviewed-by: Stefan Neufeind <typo3.neufeind@speedpartner.de>
Tested-by: Stefan Neufeind <typo3.neufeind@speedpartner.de>