Implement EIP-2565

[timbeiko]

Implement EIP-2565 using Option 2 (see: https://eips.ethereum.org/EIPS/eip-2565#specification)

PoC implementation by Danno: shemnon@f7b1824

[timbeiko]

Test vectors: https://gist.github.com/hellosupranational/93c5d87b9ba75464590fc8ec765184e1

[timbeiko]

Martin's comments: ethereum/EIPs#2955

[shemnon]

old impl on dead branch - shemnon@f7b1824

[davemec]

Benchmark results from changes:

ModEXP eip_example1 for 804 gas. Charging 1,360 gas.
ModEXP eip_example2 for 33 gas. Charging 1,360 gas.
ModEXP nagydani-1-square for 99 gas. Charging 200 gas.
ModEXP nagydani-1-qube for 111 gas. Charging 200 gas.
ModEXP nagydani-1-pow0x10001 for 189 gas. Charging 341 gas.
ModEXP nagydani-2-square for 197 gas. Charging 200 gas.
ModEXP nagydani-2-qube for 192 gas. Charging 200 gas.
ModEXP nagydani-2-pow0x10001 for 471 gas. Charging 1,365 gas.
ModEXP nagydani-3-square for 486 gas. Charging 341 gas.
ModEXP nagydani-3-qube for 534 gas. Charging 341 gas.
ModEXP nagydani-3-pow0x10001 for 1,362 gas. Charging 5,461 gas.
ModEXP nagydani-4-square for 1,410 gas. Charging 1,365 gas.
ModEXP nagydani-4-qube for 1,684 gas. Charging 1,365 gas.
ModEXP nagydani-4-pow0x10001 for 4,832 gas. Charging 21,845 gas.
ModEXP nagydani-5-square for 4,318 gas. Charging 5,461 gas.
ModEXP nagydani-5-qube for 5,185 gas. Charging 5,461 gas.
ModEXP nagydani-5-pow0x10001 for 18,612 gas. Charging 87,381 gas.