RFR: 8043537: Changes for JDK-8039951 introduced circular dependency between Kerberos and com.sun.security.auth

[Wang Weijun]

Hi All

Please review the code changes at

  http://cr.openjdk.java.net/~weijun/8043537/webrev.02/

The fix creates geteuid() in sun.misc.VM so DflCache.java does not depend on 
JAAS modules anymore. Alan suggested me to add some similar methods so other 
people can use it.

Thanks
Max