fix shmdt syscall calling convention on old archs

src/ipc/shmdt.c

@@ -7,6 +7,6 @@ int shmdt(const void *addr)
 #ifdef SYS_shmdt
 	return syscall(SYS_shmdt, addr);
 #else
-	return syscall(SYS_ipc, IPCOP_shmdt, addr);
+	return syscall(SYS_ipc, IPCOP_shmdt, 0, 0, 0, addr);
 #endif
 }