Xserver/os/connection.c: Only define XSERV_t, TRANS_SERVER and TRANS_REOPEN if not yet defined.

nx-X11/programs/Xserver/os/connection.c

@@ -72,9 +72,15 @@ SOFTWARE.
 #endif
 #include <nx-X11/X.h>
 #include <nx-X11/Xproto.h>
-#define XSERV_t
-#define TRANS_SERVER
-#define TRANS_REOPEN
+#ifndef XSERV_t
+# define XSERV_t
+#endif
+#ifndef TRANS_SERVER
+# define TRANS_SERVER
+#endif
+#ifndef TRANS_REOPEN
+# define TRANS_REOPEN
+#endif
 #include <nx-X11/Xtrans/Xtrans.h>
 #include <errno.h>
 #include <signal.h>