Lock down maven plugin versions

This prevents surprises by implicit updates to newer versions.

Change-Id: I06508036d468fa5299ea774e26a73312bb286ec2
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
diff --git a/pom.xml b/pom.xml
index 2e57e6f..9e4e281 100644
--- a/pom.xml
+++ b/pom.xml
@@ -142,7 +142,8 @@
       <plugins>
         <plugin>
           <groupId>org.apache.maven.plugins</groupId>
-          <artifactId>maven-jar-plugin</artifactId>
+	  <artifactId>maven-jar-plugin</artifactId>
+          <version>2.3</version>
           <configuration>
             <archive>
               <manifestEntries>
@@ -185,6 +186,18 @@
         </plugin>
 
         <plugin>
+          <groupId>org.apache.maven.plugins</groupId>
+          <artifactId>maven-source-plugin</artifactId>
+          <version>2.1.1</version>
+        </plugin>
+
+	<plugin>
+          <groupId>org.apache.maven.plugins</groupId>
+          <artifactId>maven-javadoc-plugin</artifactId>
+	  <version>2.6.1</version>
+        </plugin>
+
+        <plugin>
           <groupId>org.codehaus.mojo</groupId>
           <artifactId>build-helper-maven-plugin</artifactId>
           <version>1.3</version>