This reverts commit 5c949d3b.

Package fdtrack logs statistics about open file descriptors.
This should help identify the source of #1549.

The JSON-RPC server wraps TCP connections in order to be able to shut
down them down when RPC is stopped. This is rather scary code. Go 1.3
introduced the http.Server.ConnState hook for such purposes. We can use
this facility now that we depend on Go 1.4.

There are multiple reasons for the switch apart from making the code
less scary:

* the TCP listener no longer ticks every second to check a channel
* pending requests are allowed to finish after stopping the server
* we can time out idle keep-alive connections

bugfix, pending transaction was resend with new gas price/limit but not removed from transaction pool

I forgot to update one instance of "go-ethereum" in commit 3f047be5.

All code outside of cmd/ is licensed as LGPL. The headers
now reflect this by calling the whole work "the go-ethereum library".

registry initialisers now return the txhash which caller can use to retrieve receipt

* resolver -> common/registrar
  * global registrar name registry interface
  * add Call to resolver backend interface
  * the hashReg and UrlHing contracts now initialised from global registry
  * initialization of contracts uniform
  * improve errors and more econsistent method names
* common/registrar/ethreg: versioned registrar
* integrate new naming and registrar in natspec
* js console api: setGlobalRegistrar, setHashReg, setUrlHint
* js test TestContract uses mining - tests fixed all pass
* eth/backend: allow PoW test mode (small ethash DAG)
* console jsre refers to resolver.abi/addr,
* cmd/geth/contracts.go moved to common/registrar

* resolver -> common/registrar
  * global registrar name registry interface
  * add Call to resolver backend interface
  * the hashReg and UrlHing contracts now initialised from global registry
  * initialization of contracts uniform
  * improve errors and more econsistent method names
* common/registrar/ethreg: versioned registrar
* integrate new naming and registrar in natspec
* js console api: setGlobalRegistrar, setHashReg, setUrlHint
* js test TestContract uses mining - tests fixed all pass
* eth/backend: allow PoW test mode (small ethash DAG)
* console jsre refers to resolver.abi/addr,
* cmd/geth/contracts.go moved to common/registrar

Added some additional backward compatibility code for old receipts