Currently, the JVM implementation of JVM_DefineModule(..., jobjectArray packages) checks that 'packages' does not contain any duplicates. For example, if 'packages' contained p1, p2, p1 then the JVM would detect the duplicate p1's and throw an IAE. Let's remove this check because it is potentially expensive and not that beneficial to the user. Instead, the JVM would just ignore any duplicates.

The JVM would still check that the packages are not in any already defined module for the loader. This check would not change.