Add support for bound functions with user data pointers

[akrieger]

https://github.com/tbluemel/quickjscpp/blob/master/patches/2024-01-13/0001-Add-C-Closures.patch implements functions bound with user data pointers directly, instead of requiring packing data into runtime tracked JSValue's. I think this would be a useful to have in quickjs-ng.

[bnoordhuis]

Seems useful. PR welcome.

[akrieger]

I am checking with the author that my approach is acceptable (tbluemel/quickjscpp#3), and then I will do so.