ipc.h: fix gnu aliases for key and seq in struct ipc_perm

the macro was the wrong way round, additionally GNU defines
__ prefixed versions, which are used by qemu.

include/sys/ipc.h

@@ -14,8 +14,10 @@ extern "C" {
 #include <bits/alltypes.h>
 
 #ifdef _GNU_SOURCE
-#define __ipc_perm_key key
-#define __ipc_perm_seq seq
+#define key __ipc_perm_key
+#define seq __ipc_perm_seq
+#define __key __ipc_perm_key
+#define __seq __ipc_perm_seq
 #endif
 
 #include <bits/ipc.h>