darosior

(Contains input from many people, not my own ideas)

Notes

• Forbid multi, have a new multi_a itself forbidden in other contexts
• We now need to care about the maximum stack size (1000). With Taproot it's now also checked before executing the Script.
• We could have a new d: wrapper that is u because the MINIMALIF rule is consensus
• It doesn't look like there is interesting combinations of the new CHECKSIGADD opcode with existing fragment. Maybe we could have used it for thresh to save an OP_ADD if the sub was a CHECKSIG, but the arguments aren't in the right order for this.
• No need to check for the Script size anymore
• I don't think we need to take the sigop budget into account, as we can't create a Script that would duplicate the signatures.
• When calculating sizes, keep in mind the signature length is now 64