scontinue use of JavaScript's Date.toGMTString with an
implementation that will always match the format specified in
java.util.Date's JavaDocs. This resolves issue 1099.

Patch by: bobv
Review by: jgw
Issue: 1099



git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@1202 8db76d5a-ed1c-0410-87a9-c151d255dfc7