Enable Tomcat to work in a OSGI environment with alternative Servlet and JSP API JARs.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1577315 13f79535-47bb-0310-9956-ffa450edef68
Simplify

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1577324 13f79535-47bb-0310-9956-ffa450edef68