Homestead Release Candidate

(cherry picked from commit e22fd22c97b4f5d4af118dca3fb2cb6292a520a6)

Conflicts:
	cmd/utils/flags.go

(cherry picked from commit ab92678f)

(cherry picked from commit 64ee5763)

Turns out we actually don't need it, USE_NUM_NONE works
because we also set USE_FIELD_INV_BUILTIN.

Conflicts:
	Makefile
	crypto/secp256k1/secp256.go

Fixes #2201
(cherry picked from commit 26e72b2c)

When a block is queried for retrieval we should add a check whether the
block falls within the frontier rules. If we'd always use `From`
retrieving transaction might fail. This PR temporarily changes
everything to `FromFrontier` (safe!).

This is a backport of c616391d

This commit increases the artificial gas floor to 4712388
(cherry picked from commit f954a8b6)

Assuming the following scenario where a miner has 15% of all hashing
power and the ability to exert a moderate control over the network to
the point where if the attacker sees a message A, it can't stop A from
propagating, but what it **can** do is send a message B and ensure that
most nodes see B before A. The attacker can then selfish mine and
augment selfish mining strategy by giving his own blocks an advantage.

This change makes the time at which a block is received less relevant
and so the level of control an attacker has over the network no longer
makes a difference.

This change changes the current td algorithm `B_td > C_td` to the new
algorithm `B_td > C_td || B_td == C_td && rnd < 0.5`.

* Removed some strange code that didn't apply state reverting properly
* Refactored code setting from vm & state transition to the executioner
* Updated tests

Conflicts:
	common/registrar/ethreg/api.go
	core/tx_pool.go
	core/vm/jit_test.go

* 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

Conflicts:
	core/vm/environment.go
	crypto/crypto.go
	crypto/secp256k1/secp256.go
	eth/api.go

On Windows, UDPConn.ReadFrom returns an error for packets larger
than the receive buffer. The error is not marked temporary, causing
our loop to exit when the first oversized packet arrived. The fix
is to treat this particular error as temporary.

Fixes: #1579, #2087
Updates: #2082

Conflicts:
	p2p/discover/udp_test.go

Conflicts:
	p2p/rlpx.go

Conflicts:
	p2p/discover/udp_test.go

The s2 parameter was not actually written to the MAC.

Conflicts:
	VERSION
	cmd/geth/main.go

miner: bugfix where blockhash in receipts and logs is left empty

Update common test files

rpc/api, xeth: added signTransaction method

Makefile: individual platforms, configurable Go runtime

eth/downloader: fetch data proportionally to peer capacity

cmd/geth, cmd/utils: removed legalese

core, eth, miner, xeth: clean up tx/receipt db accessors

eth/downloader: don't hang for spurious deliveries