For DD functions that return a DdNode*, errors can be reported by returning NULL.
Functions that have no return value (printing, etc) or a data value (double, etc)
should set the flag, which can be converted into an CuddOutOfMemoryException on
the PRISM side using JDD.checkForCuddError()
git-svn-id: https://www.prismmodelchecker.org/svn/prism/prism/trunk@10474 bbc10eb1-c90d-0410-af57-cb519fbb1720