osd: Return would block when reading a socket with no data available - no error can be confused with remote shutdown.

src/devices/bus/coco/coco_dwsock.cpp

@@ -135,9 +135,9 @@ u8 beckerport_device::read(offs_t offset)
 		case DWS_STATUS:
 			if (!m_rx_pending)
 			{
-				/* Try to read from dws */
+				// Try to read from dws
 				std::error_condition filerr = m_pSocket->read(m_buf, 0, sizeof(m_buf), m_rx_pending);
-				if (filerr)
+				if (filerr && (std::errc::operation_would_block != filerr))
 					osd_printf_error("%s: coco_dwsock.c: beckerport_device::read() socket read operation failed with error %s:%d %s\n", tag(), filerr.category().name(), filerr.value(), filerr.message());
 				else
 					m_head = 0;

src/osd/modules/file/posixsocket.cpp

@@ -106,7 +106,7 @@ public:
 		{
 			// no data available
 			actual = 0;
-			return std::error_condition();
+			return std::errc::operation_would_block;
 		}
 	}
 

src/osd/modules/file/winsocket.cpp

@@ -103,7 +103,7 @@ public:
 		{
 			// no data available
 			actual = 0;
-			return std::error_condition();
+			return std::errc::operation_would_block;
 		}
 	}