additions for win32
Add WSAESOCKTNOSUPPORT in nn.h and err.c
Handle the Windows error ERROR_NOT_CONNECTED, ERROR_PIPE_NOT_CONNECTED,
ERROR_BROKEN_PIPE and ERROR_NO_DATA
Add sockaddr_un for Win32.
sockaddr_un should have the same size with sockaddr_storage.
Add HANDLE p alias for SOCKET s.
Enable IPC on Windows first.
Refactoring the IPC address retrieve code into function nn_usock_create_ipc_address
Add nn_usock_unlink for support unlink IPC pipe name.
Create function nn_usock_close to handle socket close and PIPE close at the same time.
Add win_error_check_return functin
Storage the nn_epbase parameter in usock_win for named pipe ipc usage under win32.
Fix a typo in ipc.c
Fix a miss check in nn_usock_cancel_io
Remove the warnings.
setsockopt always happens before socket connect and socket bind, that's gives use
an opportunity to implement it with Windows Named Pipe.
Force convert void* to (uint8_t*) for handle pointer add operation.

Conflicts:
	tests/zerocopy.c
Use macro instead direct literal.
Add a full functional Named Pipe under win32 with best performance.
Merge pull request #254 from lygstate/minor-fixes

Add Windows Named PIPE support.