Use ClassFormatException in ElementValue.readElementValue() as this behaviour is driven by user-provided data,
instead of logic errors in the code (as is the case for remaining RuntimeExceptions in BCEL).
This review was inspired by r1624396.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1624542 13f79535-47bb-0310-9956-ffa450edef68