Handling Duplicate Keys

[felix-gohla]

Hi and first at all thank you for providing this python wrapper!

During some tests, I noticed, that the python process hangs during populating the XOR-filter when using duplicate items. I found, that the upstream library now provides the feedback to the user when duplicate keys are recognised.

Now, I wanted to ask whether we could do the following:

• Update the upstream xor_singleheader library via the submodule.
• Allow the user to automatically de-duplicate the entries before population.

If you're fine with this, I'd be glad to contribute and issue the corresponding pull requests. 😊 🚀