base58: add paranoid return value checks
add NetworkIDString() to chainparams

- returns the BIP70 network string
- use that new function in the core and GUI code and remove unused code
  and functions
Merge pull request #4337

88df548 base58: add paranoid return value checks (Jeff Garzik)
Merge pull request #4326

f5ae6c9 add NetworkIDString() to chainparams (Philip Kaufmann)
Remove `using namespace std` from header file

It's considered bad form to import things into the global namespace in a
header. Put it in the cpp files where it is needed instead.
Merge pull request #4349

09eb201 Remove `using namespace std` from header file (Wladimir J. van der Laan)
add comment to HelpMessage() to ensure alphabetical ordering

- also rename hmm to mode, to be consistent between .h and .cpp
Merge pull request #4357

1020f59 add comment to HelpMessage() to ensure alphabetical ordering (Philip Kaufmann)
Get rid of Params().RPCisTestNet()
Add "chain" to getmininginfo, improve help in getblockchaininfo
Merge pull request #4333

f6984e8 Add "chain" to getmininginfo, improve help in getblockchaininfo (jtimon)
b82b7ec Get rid of Params().RPCisTestNet() (jtimon)
rework closesocket()

- make closesocket() the pure Win32 API call on Win32
- make closesocket() emulate the Win32 behaviour on all other OSes
extend and cleanup use of closesocket()

- add missing closesocket() calls for BindListenPort()
- always call closesocket() before printing any text (ensure consistent
  usage in the code)

misc small changes in net:
- remove unused CNode::Cleanup()
- add missing vhListenSocket.clear() to ~CNetCleanup()

changes in ConnectSocketDirectly() unrelated to closesocket():
- replace 3 following calls to WSAGetLastError() by storing result into
  nErr and use this in an if-clause
- convert an if() to an else if(), which removes an unneded check if the
  first case is true