Snipping JRE 1.5 hostile Override annotations from UserAgentAsserter
patch.  We only just deprecated 1.5, need to be friendly for one more
relese.

Review at http://gwt-code-reviews.appspot.com/1334801

Review by: fredsa@google.com

git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@9646 8db76d5a-ed1c-0410-87a9-c151d255dfc7