RPC client option: -rpcwait, to wait for server start
Provide build time when building from tarball:

 When building from tarball (i.g. not from git source tree or when git
 is not available) `genbuild.sh` write undefined $TIME to "build/build.h".

 Even worse, when TIME is set in the environment then its value
 is written instead of a date.

 For me this change fixed FTBFS which I got because I had
 TIME enviroment variable set with format for time(1) utility.
Merge pull request #3283 from gavinandresen/rpcwait

RPC client option: -rpcwait, to wait for server start
Merge pull request #3293 from onlyjob/master

Provide build time when building from tarball:
Split up bitcoinrpc (code movement only)

Split bitcoinrpc up into

- rpcserver: bitcoind RPC server
- rpcclient: bitcoin-cli RPC client
- rpcprotocol: shared common HTTP/JSON-RPC protocol code

One step towards making bitcoin-cli independent from the rest
of the code, and thus a smaller executable that doesn't have to
be linked against leveldb.

This commit only does code movement, there are no functional changes.