Fixing the javadoc build breaks.  One problem is that the doc/build.xml
has drifted stale against user/build.xml's classpath (we should unify
them, but the goal here is to fix the break); another is citing
@examples that don't (yet) exist.

Review at http://gwt-code-reviews.appspot.com/963801

Review by: jlabanca@google.com

git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@8949 8db76d5a-ed1c-0410-87a9-c151d255dfc7