Update maven compiler to 2.3.2

This change removes a redundant addition of source encoding and makes our
compiler match the current maven default. This amends the commit
4775b25a5932a2a24da2c55356936e2f98bff98c

Upstream issue http://jira.codehaus.org/browse/MCOMPILER-70

pom.xml

@@ -276,11 +276,10 @@
       <plugin>
         <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-compiler-plugin</artifactId>
-        <version>2.0.2</version>
+        <version>2.3.2</version>
         <configuration>
           <source>1.6</source>
           <target>1.6</target>
-          <encoding>${project.build.sourceEncoding}</encoding>
         </configuration>
       </plugin>
       <plugin>