Return two fixes from previous backout which does not require

review by secteam@ for the reasons mentioned below.

1) Rename /dev/urandom to /dev/random since urandom marked as
XXX Deprecated
alias in /sys/dev/random/randomdev.c
(this is our naming convention and no review by secteam@ required)

2) Set rs_stired flag after forced initialization to prevent
double stearing.
(this is already in OpenBSD, i.e. they don't have double stearing.
It means that this change matches their code path and no additional
secteam@ review required)

Submitted by:   Thorsten Glaser <tg@mirbsd.de> (2)

lib/libc/gen/arc4random.c

@@ -54,7 +54,7 @@ struct arc4_stream {
 
 static pthread_mutex_t	arc4random_mtx = PTHREAD_MUTEX_INITIALIZER;
 
-#define	RANDOMDEV	"/dev/urandom"
+#define	RANDOMDEV	"/dev/random"
 #define KEYSIZE		128
 #define	THREAD_LOCK()						\
 	do {							\
@@ -193,6 +193,7 @@ arc4random_stir(void)
 	THREAD_LOCK();
 	arc4_check_init();
 	arc4_stir();
+	rs_stired = 1;
 	THREAD_UNLOCK();
 }