Adding support for WS-Security kerberos credential delegation + a system test

Conflicts:
	rt/ws/security/src/main/java/org/apache/cxf/ws/security/SecurityConstants.java
	rt/ws/security/src/main/java/org/apache/cxf/ws/security/kerberos/KerberosClient.java
	rt/ws/security/src/main/java/org/apache/cxf/ws/security/wss4j/WSS4JInInterceptor.java
	services/sts/systests/advanced/src/test/java/org/apache/cxf/systest/sts/kerberos/KerberosTokenTest.java
	services/sts/systests/advanced/src/test/resources/org/apache/cxf/systest/sts/kerberos/cxf-service.xml
Recording .gitmergeinfo Changes
Fixing build
Fixing build II