Added currentSpan

Set currentSpan from addSpan()
Added getCurrSpanRefArea


git-svn-id: https://svn.apache.org/repos/asf/xmlgraphics/fop/branches/FOP_0-20-0_Alt-Design@197588 13f79535-47bb-0310-9956-ffa450edef68

src/java/org/apache/fop/area/MainReferenceArea.java

 extends AbstractReferenceArea
 implements ReferenceArea {
     private List spanAreas = new ArrayList();
-
+    private SpanReferenceArea currentSpan = null;
     /**
      * @param parent
      * @param sync
      */
     public void addSpan(SpanReferenceArea span) {
         spanAreas.add(span);
+        currentSpan = span;
     }
 
+    public SpanReferenceArea getCurrSpanRefArea() {
+        return currentSpan;
+    }
     /**
      * Get the span areas from this area.
      *