renable slow tests

these tests are only slow with cobertura enabled

core/java/build.xml

@@ -230,10 +230,12 @@
                     <exclude name="**/ElGamalAESEngineTest.java" />
                     <exclude name="**/StructureTest.java" />
                     <!-- temporarily  exclude slow tests -->
+                    <!-- let's now temporarily exclude the exclusions
                     <exclude name="**/HMACSHA256Test.java" />
                     <exclude name="**/SHA1HashTest.java" />
                     <exclude name="**/SHA256Test.java" />
                     <exclude name="**/DataHelperTest.java" />
+                    -->
                     <!-- end of slow tests -->
                 </fileset>
             </batchtest>