Add build-helper-maven-plugin in pom.xml

This helps to get the generated antlr sources included in the
build in Eclipse.

Change-Id: I78962ea705b2b5bd406e19df3c1bd1e6cf6d2c74

.settings/org.eclipse.core.resources.prefs

diff --git a/.settings/org.eclipse.core.resources.prefs b/.settings/org.eclipse.core.resources.prefs
index 5b781ec..db8e760 100644
--- a/.settings/org.eclipse.core.resources.prefs
+++ b/.settings/org.eclipse.core.resources.prefs
@@ -1,3 +1,4 @@
 eclipse.preferences.version=1
 encoding//src/main/java=UTF-8
 encoding//src/test/java=UTF-8
+encoding//target/generated-sources/antlr=UTF-8

pom.xml

diff --git a/pom.xml b/pom.xml
index b1a8b51..80e19cc 100644
--- a/pom.xml
+++ b/pom.xml
@@ -350,6 +350,25 @@
           </execution>
         </executions>
       </plugin>
+      <plugin>
+        <groupId>org.codehaus.mojo</groupId>
+        <artifactId>build-helper-maven-plugin</artifactId>
+        <version>1.7</version>
+        <executions>
+          <execution>
+            <id>add-antlr-source</id>
+            <phase>generate-sources</phase>
+            <goals>
+              <goal>add-source</goal>
+            </goals>
+            <configuration>
+              <sources>
+                <source>target/generated-sources/antlr</source>
+              </sources>
+            </configuration>
+          </execution>
+        </executions>
+      </plugin>
     </plugins>
     <extensions>
       <extension>