Remove implementation of disabled opcodes

[gavinandresen]

So we stop getting pull requests (like #2604) fixing problems with disabled Script opcodes.
A hard fork would be required to re-enable these, and if we ever did that we'd require extensive review and testing.

I double-checked to make sure the script_invalid.json unit tests make sure that the disabled opcodes are handled properly (script invalid even if the disabled opcodes are in the unexecuted branch of an OP_IF); they do.

[luke-jr]

Any reason not to remove the definitions of OP_disabledops entirely?

[sipa]

The only reason to keep them would be backward compatibility for the decoded version, I guess, and then even only for very weird scripts...

[BitcoinPullTester]

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[laanwj]

Good. The code is unused and there is no reason to keep it like this. If it is ever decided to bring the opcodes back, it can be done with better designed semantics w.r.t signed/unsigned handling.

[petertodd]

@luke-jr The code that actually disabled those OP's is executed, so I'd be inclined to leave that in place out of paranoia, at least for now.

FWIW, I manually reviewed the change.

[gavinandresen]

RE: remove opcodes entirely: I thought about removing the OP_ enum constants, but then we'd just have to use hard-coded 0x constants in a couple of places (the early if statement, and the opcode-to-string map so unit tests continued working) which would be uglier and more error-prone.

[sipa]

ACK