[BUGFIX] softrefproc typolink lacks support for separation by line feed

Since #24121 the field content in "image_link" is separated by line
feeds instead of commas. Since then the soft reference processor
for "typolink[linkList]" is broken for this field. This results in broken
image links in imports and exports and possible unchecked links in
linkvalidator extension. In 4.7 this applies also for the field
"longdescURL".

This have not to be fixed for versions later than 4.7, because since 6.0
the fields "image_link" and "longdescURL" aren't used anymore.

Resolves: #57006
Releases: 4.7, 4.5
Change-Id: I3a070d4d6e24b60a0658ec5bb6cc77d26a3e2f2d
Reviewed-on: http://review.typo3.org/28483
Reviewed-by: Markus Klein <klein.t3@reelworx.at>
Tested-by: Markus Klein <klein.t3@reelworx.at>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>