Add multi-release to API and Core manifests

Author: ppkarwasz

log4j-api/pom.xml

@@ -33,6 +33,11 @@
     <javadoc.skip>false</javadoc.skip>
     <!-- TODO: fix errors an reenable SpotBugs -->
     <spotbugs.skip>true</spotbugs.skip>
+
+    <!--
+      ~ OSGi and JPMS options
+      -->
+    <bnd-multi-release>true</bnd-multi-release>
   </properties>
   <dependencies>
     <dependency>

log4j-core/pom.xml

@@ -33,6 +33,11 @@
     <javadoc.skip>false</javadoc.skip>
     <!-- TODO: fix errors an reenable SpotBugs -->
     <spotbugs.skip>true</spotbugs.skip>
+
+    <!--
+      ~ OSGi and JPMS options
+      -->
+    <bnd-multi-release>true</bnd-multi-release>
   </properties>
   <dependencies>
     <dependency>