EIP-7907: Meter Contract Code Size And Increase Limit

[jgresham]

https://github.com/ethereum/EIPs/blob/master/EIPS/eip-7907.md
tldr; increases the hard contract code size limit from 24KB (24576 bytes) introduced in EIP-170 to 256KB

It is Considered for Inclusion for Fusaka. The EIP also changes how gas is calculated for specific cases.

Eth Magicians thread: https://ethereum-magicians.org/t/eip-7907-meter-contract-code-size-and-increase-limit/23156/14
Geth PR (WIP): qizhou/go-ethereum#1