w32: Move defines for socket specific errors to qemu-os-win32.h

As those defines are only used for w32,
they should be in the header file for w32.

All files which include slirp.h or qemu_socket.h also
include qemu-os-win32.h.

Signed-off-by: Stefan Weil <sw@weilnetz.de>
diff --git a/slirp.h b/slirp.h
index 8491aa2..26e327a 100644
--- a/slirp.h
+++ b/slirp.h
@@ -15,18 +15,6 @@
 #include <sys/timeb.h>
 #include <iphlpapi.h>
 
-#undef EWOULDBLOCK
-#undef EINPROGRESS
-#undef ENOTCONN
-#undef EHOSTUNREACH
-#undef ENETUNREACH
-#undef ECONNREFUSED
-#define EWOULDBLOCK WSAEWOULDBLOCK
-#define EINPROGRESS WSAEINPROGRESS
-#define ENOTCONN WSAENOTCONN
-#define EHOSTUNREACH WSAEHOSTUNREACH
-#define ENETUNREACH WSAENETUNREACH
-#define ECONNREFUSED WSAECONNREFUSED
 #else
 #define ioctlsocket ioctl
 #define closesocket(s) close(s)