absorb final CLASSPATH as well, such that tools might provide that by elementary means, without the "classpath" shell function (e.g. kodkodi/nitpick);

--- a/lib/Tools/java	Thu Sep 12 18:53:51 2013 +0200
+++ b/lib/Tools/java	Thu Sep 12 20:53:25 2013 +0200
@@ -6,6 +6,9 @@
 
 declare -a JAVA_ARGS; eval "JAVA_ARGS=($ISABELLE_JAVA_SYSTEM_OPTIONS)"
 
+[ -n "$CLASSPATH" ] && classpath "$CLASSPATH"
+unset CLASSPATH
+
 isabelle_jdk java "${JAVA_ARGS[@]}" \
   -classpath "$(jvmpath "$ISABELLE_CLASSPATH")" "$@"