sw: don't assert when SwXBookmark creates duplicate CrossRef*Bookmark
sw: don't assert when SwXBookmark creates duplicate CrossRef*Bookmark

The bugdoc of fdo#87110 has a couple such duplicates.  Check for it and
let SwXBookmark throw an IllegalArgumentException.

Change-Id: I460dc3a8d9c554c194a32a73526e13422ddd1c52

JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core