64 bit arithmetic soft fork

Dovetailing this, if a new developer comes to the project and wants to do some simple numerical computations in Script they currently have to learn about policy (SCRIPT_VERIFY_MINIMALDATA). How great would it be to be able to remove policies (reduce complexity, imo) with this change.

Perhaps this could also include removing the SCRIPT_VERIFY_MINIMALIF as well.

‘Removing’ is probably a strong word, but no longer having to take these policy flags into account for future soft forks.