With this commit, core/state's access to the underlying key/value database is
mediated through an interface. Database errors are tracked in StateDB and
returned by CommitTo or the new Error method.

Motivation for this change: We can remove the light client's duplicated copy of
core/state. The light client now supports node iteration, so tracing and storage
enumeration can work with the light client (not implemented in this commit).

* accounts/abi: reorganizing package and some notes and a quick correction of name.

Signed-off-by: RJ Catalano <rj@monax.io>

get rid of some imports

Signed-off-by: RJ Catalano <rj@monax.io>

* accounts/abi: move file names

Signed-off-by: RJ Catalano <rj@monax.io>

* accounts/abi: fix boolean decode function

Signed-off-by: RJ Catalano <rj@monax.io>

* accounts/abi: fix for the array set and for creating a bool

Signed-off-by: RJ Catalano <rj@monax.io>

* accounts/abi: be very very very correct

Signed-off-by: RJ Catalano <rj@monax.io>

* accounts/abi: fix up error message and variable names

Signed-off-by: RJ Catalano <rj@monax.io>

* accounts/abi: take out unnecessary argument in pack method

Signed-off-by: RJ Catalano <rj@monax.io>

* accounts/abi: add bool unpack test and add a panic to readBool function

Signed-off-by: RJ Catalano <rj@monax.io>

* accounts/abi: fix panic message

Signed-off-by: RJ Catalano <rj@monax.io>

* accounts/abi: change from panic to basic error

Signed-off-by: RJ Catalano <rj@monax.io>

* accounts/abi: fix nil to false

Signed-off-by: RJ Catalano <rj@monax.io>

* accounts/abi: fill out type regex tests and fill with the correct type for integers

Signed-off-by: RJ Catalano <rj@monax.io>

* accounts/abi: move packNumbers into pack.go.

Signed-off-by: RJ Catalano <rj@monax.io>

* accounts/abi: separation of the testing suite into appropriately named files.

Signed-off-by: RJ Catalano <rj@monax.io>

* account/abi: change to hex string tests.

Signed-off-by: RJ Catalano <rj@monax.io>

* account/abi: fix up rest of tests to hex

Signed-off-by: RJ Catalano <rj@monax.io>

* accounts/abi: declare bool at the package level

Signed-off-by: RJ Catalano <rj@monax.io>

* accounts/abi: use errors package in the error file.

Signed-off-by: RJ Catalano <rj@monax.io>

* accounts/abi: fix ugly hack and fix error type declaration.

Signed-off-by: RJ Catalano <rj@monax.io>

* consensus, core, ethstats: use engine specific block beneficiary

* core, eth, les, miner: use explicit beneficiary during mining

This commit adds pluggable consensus engines to go-ethereum. In short, it
introduces a generic consensus interface, and refactors the entire codebase to
use this interface.

This commit solves several issues concerning the genesis block:

* Genesis/ChainConfig loading was handled by cmd/geth code. This left
  library users in the cold. They could specify a JSON-encoded
  string and overwrite the config, but didn't get any of the additional
  checks performed by geth.
* Decoding and writing of genesis JSON was conflated in
  WriteGenesisBlock. This made it a lot harder to embed the genesis
  block into the forthcoming config file loader. This commit changes
  things so there is a single Genesis type that represents genesis
  blocks. All uses of Write*Genesis* are changed to use the new type
  instead.
* If the chain config supplied by the user was incompatible with the
  current chain (i.e. the chain had already advanced beyond a scheduled
  fork), it got overwritten. This is not an issue in practice because
  previous forks have always had the highest total difficulty. It might
  matter in the future though. The new code reverts the local chain to
  the point of the fork when upgrading configuration.

The change to genesis block data removes compression library
dependencies from package core.

There is no need to depend on the old context package now that the
minimum Go version is 1.7. The move to "context" eliminates our weird
vendoring setup. Some vendored code still uses golang.org/x/net/context
and it is now vendored in the normal way.

This change triggered new vet checks around context.WithTimeout which
didn't fire with golang.org/x/net/context.

* accounts, cmd, eth, ethdb: port logs over to new system

* ethdb: drop concept of cache distribution between dbs

* eth: fix some log nitpicks to make them nicer

* common/math: optimize PaddedBigBytes, use it more

name              old time/op    new time/op    delta
PaddedBigBytes-8    71.1ns ± 5%    46.1ns ± 1%  -35.15%  (p=0.000 n=20+19)

name              old alloc/op   new alloc/op   delta
PaddedBigBytes-8     48.0B ± 0%     32.0B ± 0%  -33.33%  (p=0.000 n=20+20)

* all: unify big.Int zero checks

Various checks were in use. This commit replaces them all with Int.Sign,
which is cheaper and less code.

eg templates:

    func before(x *big.Int) bool { return x.BitLen() == 0 }
    func after(x *big.Int) bool  { return x.Sign() == 0 }

    func before(x *big.Int) bool { return x.BitLen() > 0 }
    func after(x *big.Int) bool  { return x.Sign() != 0 }

    func before(x *big.Int) int { return x.Cmp(common.Big0) }
    func after(x *big.Int) int  { return x.Sign() }

* common/math, crypto/secp256k1: make ReadBits public in package math

* common: remove CurrencyToString

Move denomination values to params instead.

* common: delete dead code

* common: move big integer operations to common/math

This commit consolidates all big integer operations into common/math and
adds tests and documentation.

There should be no change in semantics for BigPow, BigMin, BigMax, S256,
U256, Exp and their behaviour is now locked in by tests.

The BigD, BytesToBig and Bytes2Big functions don't provide additional
value, all uses are replaced by new(big.Int).SetBytes().

BigToBytes is now called PaddedBigBytes, its minimum output size
parameter is now specified as the number of bytes instead of bits. The
single use of this function is in the EVM's MSTORE instruction.

Big and String2Big are replaced by ParseBig, which is slightly stricter.
It previously accepted leading zeros for hexadecimal inputs but treated
decimal inputs as octal if a leading zero digit was present.

ParseUint64 is used in places where String2Big was used to decode a
uint64.

The new functions MustParseBig and MustParseUint64 are now used in many
places where parsing errors were previously ignored.

* common: delete unused big integer variables

* accounts/abi: replace uses of BytesToBig with use of encoding/binary

* common: remove BytesToBig

* common: remove Bytes2Big

* common: remove BigTrue

* cmd/utils: add BigFlag and use it for error-checked integer flags

While here, remove environment variable processing for DirectoryFlag
because we don't use it.

* core: add missing error checks in genesis block parser

* common: remove String2Big

* cmd/evm: use utils.BigFlag

* common/math: check for 256 bit overflow in ParseBig

This is supposed to prevent silent overflow/truncation of values in the
genesis block JSON. Without this check, a genesis block that set a
balance larger than 256 bits would lead to weird behaviour in the VM.

* cmd/utils: fixup import

* vendor: add github.com/btcsuite/btcd/btcec

* crypto: add btcec fallback for sign/recover without cgo

This commit adds a non-cgo fallback implementation of secp256k1
operations.

* crypto, core/vm: remove wrappers for sha256, ripemd160

- Handle a data race where a Ledger drops between list and open
- Prolong Ledger tx confirmation window to 30 days from 1 minute
- Simplify Ledger chainid-signature calculation and validation
- Simplify Ledger USB APDU request chunking algorithm
- Silence keystore account cache notifications for manual actions
- Only enable self derivations if wallet open succeeds

Signed-off-by: DiSiqueira <dieg0@live.com>

Gas estimation currently mostly works, but can underestimate for more funky
refunds. This is because various ops (e.g. CALL) need more gas to run than they
actually consume (e.g. 2300 stipend that is refunded if not used). With more
intricate contract interplays, it becomes almost impossible to return a proper
value to the user.

This commit swaps out the simplistic gas estimation to a binary search approach,
honing in on the correct gas use. This does mean that gas estimation needs to
rerun the transaction log(max-price) times to measure whether it fails or not,
but it's a price paid by the transaction issuer, and it should be worth it to
support proper estimates.