[lang] replace clirr with japicmp

[Charles Honton]

Now that lang is compiled with java6, clirr is broken.  Do we want to update to 
a more modern report like japicmp <https://siom79.github.io/japicmp/>?

The pom change is something like 

  <plugin>
   <groupId>com.github.siom79.japicmp</groupId>
   <artifactId>japicmp-maven-plugin</artifactId>
   <version>0.8.0</version>
   <configuration>
    <parameter>
     <onlyModified>true</onlyModified>
     
<breakBuildOnBinaryIncompatibleModifications>true</breakBuildOnBinaryIncompatibleModifications>
    </parameter>
   </configuration>
   <executions>
    <execution>
     <phase>verify</phase>
     <goals>
      <goal>cmp</goal>
     </goals>
    </execution>
   </executions>
  </plugin>

regards,
chas