define classpath order of WEB-INF/lib

Currently the order in which the classpath is build by the contents of WEB-INF/lib is not defined whereas in a Maven pom classpath order is defined by the order of dependeny elements. So, e.g. a Spring boot application might fail to work when deployed as a war.
There should be an element in web.xml to define classpath order (e.g. alphabetically or by an explicit list).
See also these discussions:
https://stackoverflow.com/questions/4466526/order-of-class-loading-from-a-war-file
https://stackoverflow.com/questions/2021227/control-the-classpath-ordering-of-jars-in-web-inf-lib-on-tomcat-5/49495222#49495222

Start with the web.xml deployment descriptor and the WEB-INF/lib behavior described in the issue, then review the linked classpath-order discussions. Done means the Servlet specification clearly defines a web.xml mechanism and its ordering semantics for WEB-INF/lib, with compatibility expectations documented.

Written by the indexing model from the issue text.