p2p: fix value of DiscSubprotocolError

cmd/geth: remove spaces in client identifier

We had the wrong value (12) since forever.

p2p/discover: fix two major bugs in reply packet handling

web3: updated

cmd/ethtest: added trace flag for debugging

If the timeout fired (even just nanoseconds) before the deadline of the
next pending reply, the timer was not rescheduled. The timer would've
been rescheduled anyway once the next packet was sent, but there were
cases where no next packet could ever be sent due to the locking issue
fixed in the previous commit.

As timing-related bugs go, this issue had been present for a long time
and I could never reproduce it. The test added in this commit did
reproduce the issue on about one out of 15 runs.

Table.mutex was being held while waiting for a reply packet, which
effectively made many parts of the whole stack block on that packet,
including the net_peerCount RPC call.

core, eth, trie, xeth: merged state, chain, extra databases in one

cmd/utils, core: disable exp diff for olympic net

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