Fix https://issues.apache.org/bugzilla/show_bug.cgi?id=56829
Add the ability for users to define their own values for _RUNJAVA and _RUNJBD. Based on a patch by Neeme Praks.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1617362 13f79535-47bb-0310-9956-ffa450edef68