Remove undefined behavior from sranddev() and

srandomdev(). This doesn't actually work
with any modern C compiler:

In particular, both clang and modern gcc
verisons silently elide any xor operation
with 'junk'.

Approved by:	secteam
MFC after:	3 days

lib/libc/stdlib/rand.c

@@ -130,10 +130,9 @@ sranddev()
 
 	if (!done) {
 		struct timeval tv;
-		unsigned long junk;
 
 		gettimeofday(&tv, NULL);
-		srand((getpid() << 16) ^ tv.tv_sec ^ tv.tv_usec ^ junk);
+		srand((getpid() << 16) ^ tv.tv_sec ^ tv.tv_usec);
 	}
 }
 

lib/libc/stdlib/random.c

@@ -312,10 +312,9 @@ srandomdev(void)
 
 	if (!done) {
 		struct timeval tv;
-		volatile unsigned long junk;
 
 		gettimeofday(&tv, NULL);
-		srandom((getpid() << 16) ^ tv.tv_sec ^ tv.tv_usec ^ junk);
+		srandom((getpid() << 16) ^ tv.tv_sec ^ tv.tv_usec);
 		return;
 	}