Assume RLIMIT_STACK 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

@@ -41,9 +41,7 @@ void pwd_init (void)
 #ifdef RLIMIT_RSS
 	setrlimit (RLIMIT_RSS, &rlim);
 #endif
-#ifdef RLIMIT_STACK
 	setrlimit (RLIMIT_STACK, &rlim);
-#endif
 
 	signal (SIGALRM, SIG_IGN);
 	signal (SIGHUP, SIG_IGN);