Include org.slf4j.log4j in update site

org.slf4j.log4j is included for convenience, so that it doesn't
need to be fetched from orbit.

In newer eclipse installations, slf4j and logback itself is
already installed, only this old log4j dependency is needed.

Note: log4j is only needed to provide compatibility, see #112

Author: adangel

kepler/kepler.target

@@ -9,8 +9,6 @@
         </location>
         <location includeAllPlatforms="false" includeConfigurePhase="true" includeMode="planner" includeSource="true" type="InstallableUnit">
             <repository location="https://archive.eclipse.org/tools/orbit/downloads/drops/R20140114142710/repository/"/>
-            <unit id="org.apache.log4j" version="1.2.15.v201012070815"/>
-            <unit id="org.apache.log4j.source" version="1.2.15.v201012070815"/>
             <unit id="org.apache.commons.io" version="2.0.1.v201105210651"/>
             <unit id="org.apache.commons.io.source" version="2.0.1.v201105210651"/>
             <unit id="org.apache.commons.lang" version="2.6.0.v201205030909"/>
@@ -23,6 +21,8 @@
             <unit id="ch.qos.logback.slf4j.source" version="1.0.7.v20121108-1250"/>
             <unit id="org.slf4j.jul" version="1.7.2.v20121108-1250"/>
             <unit id="org.slf4j.jul.source" version="1.7.2.v20121108-1250"/>
+            <unit id="org.slf4j.log4j" version="1.7.2.v20130115-1340"/>
+            <unit id="org.slf4j.log4j.source" version="1.7.2.v20130115-1340"/>
         </location>
     </locations>
     <targetJRE path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-1.7"/>

net.sourceforge.pmd.eclipse/feature.xml

@@ -38,4 +38,20 @@
          install-size="0"
          version="4.14.0.qualifier"/>
 
+   <!--
+     org.slf4j.log4j is included for convenience, so that it doesn't need to be fetched from orbit.
+     Adding it here will add it to the update site of pmd-eclipse-plugin.
+     
+     In newer eclipse installations, slf4j and logback itself is already installed, only this old log4j
+     dependency is needed.
+     
+     Note: log4j is only needed to provide compatibility, see https://github.com/pmd/pmd-eclipse-plugin/pull/112
+   -->
+   <plugin
+         id="org.slf4j.log4j"
+         download-size="0"
+         install-size="0"
+         version="0.0.0"
+         unpack="false"/>
+
 </feature>