[BUGFIX] Prevent wrong ref_index for fields with soft references

If you add a page link to a field which is defined as softrefs, the
ReferenceIndex creates an index to a FAL record if there exists a file
record with the page id. As file links are always prefixed with 'file:'
this patch adds a proper check before generating a file ref_index.

Furthermore if you add a file or folder link, the field is referenced
twice for the FAL record. So we have to suppress the softreference for
those records.

Releases: master, 6.2
Resolves: #60226
Change-Id: Ieb9179d393e23eda4fdb1bb47ba4693bd92e75d9
Reviewed-on: http://review.typo3.org/37016


Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Mathias Schreiber <mathias.schreiber@wmdb.de>
Tested-by: Mathias Schreiber <mathias.schreiber@wmdb.de>
Reviewed-by: Markus Klein <klein.t3@reelworx.at>
Tested-by: Markus Klein <klein.t3@reelworx.at>