Adding clirr for reporting api differences

jetty-websocket/pom.xml

@@ -59,6 +59,23 @@
                           </archive>
                   </configuration>
             </plugin>
+            <plugin>
+              <groupId>org.codehaus.mojo</groupId>
+              <artifactId>clirr-maven-plugin</artifactId>
+              <version>2.5</version>
+              <executions>
+                <execution>
+                  <id>compare-api</id>
+                  <phase>package</phase>
+                  <goals>
+                    <goal>clirr</goal>
+                  </goals>
+                </execution>
+              </executions>
+              <configuration>
+                <comparisonVersion>9.0.3.v20130506</comparisonVersion>
+              </configuration>
+            </plugin>
         </plugins>
     </build>
 </project>