The run loop, which previously contained custom opcode executes have been
removed and has been simplified to a few checks.
Each operation consists of 4 elements: execution function, gas cost function,
stack validation function and memory size function. The execution function
implements the operation's runtime behaviour, the gas cost function implements
the operation gas costs function and greatly depends on the memory and stack,
the stack validation function validates the stack and makes sure that enough
items can be popped off and pushed on and the memory size function calculates
the memory required for the operation and returns it.
This commit also allows the EVM to go unmetered. This is helpful for offline
operations such as contract calls.
To address increasing complexity in code that handles signatures, this PR
discards all notion of "different" signature types at the library level. Both
the crypto and accounts package is reduced to only be able to produce plain
canonical secp256k1 signatures. This makes the crpyto APIs much cleaner,
simpler and harder to abuse.
* change gas cost for contract creating txs
* invalidate signature with s value greater than secp256k1 N / 2
* OOG contract creation if not enough gas to store code
* new difficulty adjustment algorithm
* new DELEGATECALL op code
* Moved `vm.Transfer` to `core` package and changed execution to call
`env.Transfer` instead of `core.Transfer` directly.
* core/vm: byte code VM moved to jump table instead of switch
* Moved `vm.Transfer` to `core` package and changed execution to call
`env.Transfer` instead of `core.Transfer` directly.
* Byte code VM now shares the same code as the JITVM
* Renamed Context to Contract
* Changed initialiser of state transition & unexported methods
* Removed the Execution object and refactor `Call`, `CallCode` &
`Create` in to their own functions instead of being methods.
* Removed the hard dep on the state for the VM. The VM now
depends on a Database interface returned by the environment. In the
process the core now depends less on the statedb by usage of the env
* Moved `Log` from package `core/state` to package `core/vm`.
