Install trigger for DAO-rescue soft-fork.

[gavofyork]

Soft-fork should only be primed to trigger if the gas-limit of
block #1760000 is at most 4,000,000.

To accomplish this we pass in the gas limit of that block to
EnvInfo so it can inform Schedule. This gets marshalled through
OpenBlock/ClosedBlock and the enact functions much like
last_hashes. block.rs's env_info() takes care to ensure
that if the current block happens to be #1760000, then we
populate with the current gas_limit.

This is a pretty awful altertation to the codebase. However, is has one huge mitigating factor:

We can revert it after block #1760000.

[debris]

tests failing

[taoeffect]

Wait, what is going on?

Please tell me I am just misunderstanding and you are not unilaterally installing a SF into Parity without any EIP and zero calls for public discussion.

Because that would be dumb. Very dumb. I'm already having to field tweets like this and seeing tweets like this. Please don't embarrass us more.

[gavofyork]

The soft fork is already in. This PR ensures it only activates if there is consensus among the Ethereum community by requiring it to trigger only if the majority form a consensus around it.

If you want to run Parity and vote against the soft-fork which prevents ETH from being drained from broken DAO contracts (i.e. you wish to help the attacker), run with --assist-dao-attack. If you would prefer to stick to the original Homestead Yellow Paper spec, even if the rest of the network goes with the soft-fork, run with --dogmatic.

[taoeffect]

@gavofyork, like many, I bought into Ethereum because of the message that you and others were selling.

Here you are giving a lecture where you describe Ethereum as a "system that cannot care":

https://www.youtube.com/watch?v=2TXk-VczNL0

And I was at Cryptoeconomicon where you gave a similar lecture pushing the same message.

Now that this system suddenly inconveniences you, you decide to do the exact opposite and change the rules so that things work out in your favor?

This is unacceptable. What do you say to those of us who supported you and Ethereum based on the message you were only just recently pushing?

[gavofyork]

Pease do not abuse PR threads for non-code-related matters. If you want to debate the finer points of consensus, pick a time when I'm less busy and have more beer.