Fix https://issues.apache.org/bugzilla/show_bug.cgi?id=56780
Enable Tomcat to start when using a IBM JRE in strict SP800-131a mode
This back-ports the fix as well as some additional changes to more closely
align the Tomcat 6 code with the code in Tomcat 7.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/tc6.0.x/trunk@1639415 13f79535-47bb-0310-9956-ffa450edef68