socket.tcp can accept fd and socket type ('master'(default), 'client')
acceptfd method can be used to write multi-threaded server.
```lua
-- main thread
local fd = srv_sock:acceptfd()
Threads.runfile('echo.lua', fd)
-- echo.lua
local fd = ...
local sock = socket.tcp(fd,'client')
```
or to interact with library such as [ESL](http://wiki.freeswitch.org/wiki/Event_Socket_Library)
```lua
local fd = srv_sock:acceptfd()
Threads.runfile('worker.lua', fd)
-- worker.lua
local sock = ESLconnection((...))
```
If we need just close fd (for example we can not run worker thread) we should call `socket.tcp(fd,'client'):close()`
inet_pton was copying the entire sockaddr_in struct,
rather than just the sin_addr field...
I am a bit unsure about the UDP fix, because it may affect
TCP as well. On UDP sockets, when a sendto fails, the next
receive/receivefrom fails with CONNRESET. I changed
sock_recv/sock_recvfrom in wsocket.c to skip the CONNRESET
from the recv/recvfrom, hoping that if the socket is TCP,
sock_waitfd will get the CONNRESET again. The tests pass,
but this should be tested more thoroughly.
Previous implementation was not making sure the socket
had the same family as the addr returned by getaddrinfo.
So instead of "connection refused", we could get "invalid
argument", which was our fault.
There seems to be a curious difference between MacOS and
Linux and I am not sure if this is documented. When you
break a "connection" on Mac OS, you only eliminate the peer
association, but the local address remains bound. On Linux,
breaking a "connection" eliminates the binding to the local
address. Have you guys ever come accross this?
Another irritating difference is that connect() returns the
error EAFNOSUPPORT on Mac OS. I am going to ignore all
errors when the reason for calling connect() is simply to
break the "connection".
