AMMediaboard: Check for EAGAIN in WSAGetLastError

[sepalani]

This PR checks on Linux for EAGAIN in case it'd be different from EWOULDBLOCK (unlikely).

Some systems might define Sockets ERRNOs as follows (e.g IBM):

Error number	Message name	Socket API type	Error description	Programmer's response
11	EAGAIN	All	There are no more processes.	Retry the operation. Data or condition might not be available at this time.
11	EAGAIN	All	TCP/IP is not active at the time of the request.	Start TCP/IP, and retry the request.
35	EWOULDBLOCK	Accept	The socket is in nonblocking mode and connections are not queued. This is not an error condition.	Reissue Accept().
35	EWOULDBLOCK	Read Recvfrom	The socket is in nonblocking mode and read data is not available. This is not an error condition.	Issue a select on the socket to determine when data is available to be read or reissue the Read()/Recvfrom().
35	EWOULDBLOCK	All receive calls (RECV, RECVMSG, RECVFROM, READV, READ), when the socket is set with the SO_RCVTIMEO socket option	The socket is in blocking mode and the receive call has blocked for the time period that was specified in the SO_RCVTIMEO option. No data was received.	The application should reissue the receive call.
35	EWOULDBLOCK	Send Sendto Write	The socket is in nonblocking mode and buffers are not available.	Issue a select on the socket to determine when data is available to be written or reissue the Send(), Sendto(), or Write().
35	EWOULDBLOCK	All send calls (SEND, SENDMSG, SENDTO, WRITEV, WRITE), when the socket is set with the SO_SNDTIMEO socket option	The socket is in blocking mode and the send call has blocked for the time period that was specified in the SO_SNDTIMEO option. No data was sent.	The application should reissue the send call.

Ready to be reviewed and tested.