OPENJPA-2381: Update SERP to 1.15.1 [JDK 8]

git-svn-id: https://svn.apache.org/repos/asf/openjpa/branches/2.2.x@1641426 13f79535-47bb-0310-9956-ffa450edef68
OPENJPA-2487: upgrade openjpa to asm5 to support java 8 [JDK 8]

git-svn-id: https://svn.apache.org/repos/asf/openjpa/branches/2.2.x@1641438 13f79535-47bb-0310-9956-ffa450edef68