Track doublespends and malleated transactions

[arnuschky]

Would be really useful. Not sure how to do it, though.

[jlopp]

I'm pretty sure that Bitcoin Core doesn't differentiate between double spends and malleated transactions; the latter is just a special case of the former.

At the moment on statoshi.info I figure that "transactions accepted - transactions received" is a good metric for rejected transactions of all types. There are a number of different rejection reasons and I'm not sure if a double spend would be rejected due to this check: https://github.com/jlopp/statoshi/blob/master/src/main.cpp#L834 or only by this check: https://github.com/jlopp/statoshi/blob/master/src/main.cpp#L866