Moved the To256
eventer: fix tests
eventer: add test for concurrent Post/Register

This test reports the race condition when run
using "go test -race".
eventer: fix data race
eth: fix filter map data race

This commit also documents (but doesn't enforce) that filters
are immutable while they're installed. This required a minor API
change.
Implemented new iterator
Merge pull request #56 from fjl/feature/raceless-eventer

Fix Eventer race
Merge pull request #57 from fjl/feature/raceless-ethereum-filters

Fix filter map race
Merge branch 'develop' of github.com-obscure:ethereum/eth-go into develop
Added generic big to 256 method. Implemented new iterator
Added some methods to comply to the PoW block interface
Implemented AR PoW
Max callstack
Refactored VM to two separate VMs; std & debug

Standard VM should be about 10x faster than the debug VM. Some error
checking has been removed, all of the log statements and therefor quite
some unnecessary if-statements.
Changed VM Test code
Tests for native function calling
Removed old installer script
Couple of minor issues fixed

* CALLVALUE pushed incorrect value to the stack
* Set execution model to closure
Working on test suite
Fixed remote Arithmetic tests