Re-roll issue 887801. Update the embedded Tomcat server and don't let callers accidentally refresh 0 oracles.

*** Original change description ***
Optimize ResourceOracle refresh by doing multiple oracles at the same time

Review at http://gwt-code-reviews.appspot.com/887801


git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@8813 8db76d5a-ed1c-0410-87a9-c151d255dfc7