proposal for destructive comparison opcode

[zack-bitcoin]

we have an opcode to check if things are equal, and it leaves those things on the stack.
This is a good optimization for using ram while processing the smart contract, but it means we are using 4 opcodes every time we check equivalence, which is something we do in practically every function.

If we also had an equivalence operator that destroyed the things after comparing them, it would save 3 bytes per comparison in a program.

[zack-bitcoin]

this is now live in the experimental branch.