Create get_socket_errno() to replace ERROR_VALUE macro eventually

src/xpdev/sockwrap.c

@@ -731,6 +731,16 @@ DLLEXPORT void set_socket_errno(int err)
 #endif
 }
 
+DLLEXPORT int get_socket_errrno(void)
+{
+#if defined(_WINSOCKAPI_)
+	int wsa_error = WSAGetLastError();
+	return wsa_error >= WSABASEERR ? wsa_error - WSABASEERR : wsa_error;
+#else
+	return errno;
+#endif
+}
+
 DLLEXPORT int xp_inet_pton(int af, const char *src, void *dst)
 {
 	struct addrinfo hints = {0};

src/xpdev/sockwrap.h

@@ -239,6 +239,7 @@ DLLEXPORT void inet_setaddrport(union xp_sockaddr *addr, uint16_t port);
 DLLEXPORT BOOL inet_addrmatch(union xp_sockaddr* addr1, union xp_sockaddr* addr2);
 DLLEXPORT char* socket_strerror(int, char*, size_t);
 DLLEXPORT void set_socket_errno(int);
+DLLEXPORT int get_socket_errno(void);
 DLLEXPORT int xp_inet_pton(int af, const char *src, void *dst);
 #if defined(_WIN32) // mingw and WinXP's WS2_32.DLL don't have inet_pton():
 	#define inet_pton	xp_inet_pton