Add missing interface classes to Private-Package to avoid unresolved package on bundle install

git-svn-id: https://svn.apache.org/repos/asf/felix/trunk@616994 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/prefs/pom.xml b/prefs/pom.xml
index f7da81b..bd4cc0d 100644
--- a/prefs/pom.xml
+++ b/prefs/pom.xml
@@ -73,6 +73,7 @@
                         </Export-Package>
                         <Private-Package>
                             org.apache.felix.prefs.impl,
+                            org.apache.commons.codec,
                             org.apache.commons.codec.binary
                         </Private-Package>
                         <Bundle-Activator>