tell pool to clear() before setting to null

Author: J38

src/edu/stanford/nlp/pipeline/StanfordCoreNLP.java

@@ -481,6 +481,8 @@ private void construct(Properties props, boolean enforceRequirements, AnnotatorI
    * release the memory associated with the annotators.
    */
   public static synchronized void clearAnnotatorPool() {
+    if (pool != null)
+      pool.clear();
     pool = null;
   }