Copy long<->base64 code to Base64Utils for server RPC code

Review at http://gwt-code-reviews.appspot.com/639801

Review by: jat@google.com

git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@8274 8db76d5a-ed1c-0410-87a9-c151d255dfc7
9 files changed