Assume SIGTTOU is defined

It is required by POSIX.1-2001.

Cc: Christian Göttsche <cgzones@googlemail.com>
Signed-off-by: Alejandro Colomar <alx@kernel.org>

libmisc/pwd_init.c

@@ -50,9 +50,7 @@ void pwd_init (void)
 	signal (SIGQUIT, SIG_IGN);
 	signal (SIGTERM, SIG_IGN);
 	signal (SIGTSTP, SIG_IGN);
-#ifdef SIGTTOU
 	signal (SIGTTOU, SIG_IGN);
-#endif
 
 	umask (077);
 }