compile warning about base64

[mkdir] Created dir: F:\temp\grouper_HEADtest\dist\build\grouper
[javac] Compiling 743 source files to F:\temp\grouper_HEADtest\dist\build\grouper
[javac] F:\temp\grouper_HEADtest\src\grouper\edu\internet2\middleware\grouper\util\GrouperUtil.java:79: warning: sun
.misc.BASE64Encoder is Sun proprietary API and may be removed in a future release
[javac] import sun.misc.BASE64Encoder;