w32: Undefine error constants before their redefinition

Avoids lots of warnings.
Signed-off-by: NJan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: NStefan Hajnoczi <stefanha@linux.vnet.ibm.com>

qemu_socket.h

@@ -8,7 +8,9 @@
 #include <ws2tcpip.h>
 
 #define socket_error() WSAGetLastError()
+#undef EWOULDBLOCK
 #undef EINTR
+#undef EINPROGRESS
 #define EWOULDBLOCK WSAEWOULDBLOCK
 #define EINTR       WSAEINTR
 #define EINPROGRESS WSAEINPROGRESS