Update maven compiler plugin to newest version (apache#1042)

* Update maven compiler plugin to newest version

The previously used version doesn't handle the errors from newer jdk
versions, so if there's a error you can't see what's actually wrong.

* Let aspectJ bind to correct phase

It was binding to process-sources before, which makes no sense since
it works on the class files. Removed the phase specification, which
allows it to bind to compile (as it does by default).

pom.xml

@@ -742,7 +742,7 @@ flexible messaging model and an intuitive client API.</description>
         </plugin>
         <plugin>
           <artifactId>maven-compiler-plugin</artifactId>
-          <version>2.3.2</version>
+          <version>3.7.0</version>
         </plugin>
         <plugin>
           <groupId>org.apache.maven.plugins</groupId>

pulsar-broker/pom.xml

@@ -246,7 +246,6 @@
         </configuration>
         <executions>
           <execution>
-            <phase>process-sources</phase>
             <goals>
               <goal>compile</goal>
             </goals>

pulsar-zookeeper/pom.xml

@@ -97,7 +97,6 @@
         </configuration>
         <executions>
           <execution>
-            <phase>process-sources</phase>
             <goals>
               <goal>compile</goal>
             </goals>