Rename ProtocolHandler to HttpUpgradeHandler

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1444946 13f79535-47bb-0310-9956-ffa450edef68
Rename canWrite() -> isReady()

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1444951 13f79535-47bb-0310-9956-ffa450edef68