cmd/geth, core/vm: setup vm settings and defaulted JIT disabled

core/vm: jit vm

string version for build server

xeth: fixed contract addr check

cmd/geth, eth: added canonical extra data

web3: regression. Fixes #1613

Reduced big int allocation by making stack items modifiable. Instead of
adding items such as `common.Big0` to the stack, `new(big.Int)` is
added instead. One must expect that any item that is added to the stack
might change.

Reduced the amount of state copied that are required by N calls by doing
a balance check prior to any state modifications.

* changed stack and removed stack ptr. Let go decide on slice reuse.

Implemented canonical extra data according to
https://github.com/ethereum/wiki/wiki/Extra-Data

miner, rpc: added submit hashrate for remote agents

xeth: added address hex check and length check

Fix tests on windows

trie: hex fix

faster hex-prefix codec and string -> []byte

They were unused and their tests failed on Windows.

Not closing the table used to be fine, but now the table has a database.

miner, core: sort txs by price, nonce

core, miner: added difficulty bomb