Disable free references reusing

Unless different instances for indirect references with same object
number but different generation numbers will be introduced, free
references reusing might be wrong. It's because indirect reference could
have been contained in some particular object (on doc reading), set free,
and then reused, while still same instance of indirect reference was
left in that particular object.

DEVSIX-608

Author: yulian-gaponenko

kernel/src/main/java/com/itextpdf/kernel/pdf/PdfXrefTable.java

@@ -181,14 +181,8 @@ PdfIndirectReference createNewIndirectReference(PdfDocument document) {
      * @return created indirect reference.
      */
     protected PdfIndirectReference createNextIndirectReference(PdfDocument document) {
-        PdfIndirectReference reference = removeFreeRefFromList(-1);
-        if (reference != null) {
-            reference.setOffset(0);
-            reference.clearState(PdfObject.FREE);
-        } else {
-            reference = new PdfIndirectReference(document, ++count);
-            add(reference);
-        }
+        PdfIndirectReference reference = new PdfIndirectReference(document, ++count);
+        add(reference);
         return reference.setState(PdfObject.MODIFIED);
     }