fix rss load. missing felix package imports

lib/felix.client.run.properties

@@ -19,6 +19,7 @@ org.osgi.framework.system.packages= org.osgi.framework; ; version=1.3.0, \
  javax.swing.filechooser; \
  org.w3c.dom; \
  org.xml.sax; \
+ org.xml.sax.ext; \
  javax.xml.parsers;\
  org.apache.xml.serialize; \
  javax.xml.transform; \

lib/felix.unit.test.properties

@@ -12,6 +12,7 @@ org.osgi.framework.system.packages= org.osgi.framework; \
  org.w3c.dom; \
  org.xml.sax; \
  org.xml.sax.helpers; \
+ org.xml.sax.ext; \
  sun.misc; \
  sun.security.action; \
  javax.xml.parsers;\

src/net/java/sip/communicator/impl/protocol/rss/rss.provider.manifest.mf

@@ -6,6 +6,7 @@ Bundle-Version: 0.0.1
 Import-Package: org.osgi.framework,
  org.xml.sax,
  org.xml.sax.helpers,
+ org.xml.sax.ext,
  org.w3c.dom,
  javax.xml.parsers,
  net.java.sip.communicator.service.configuration,