Fix boxing/unboxing by changing org.apache.logging.log4j.core.layout.RFC5424Layout.enterpriseNumber from Integer to int. A valid int is always passed in.

git-svn-id: https://svn.apache.org/repos/asf/logging/log4j/log4j2/trunk@1520022 13f79535-47bb-0310-9956-ffa450edef68