Remove xcalloc() and convert its callers to xzalloc(). About half of them

were using "1" as one of the arguments anyway, and as for the rest a multiply
and a push isn't noticeably bigger than pushing two arguments on the stack.

coreutils/ls.c

@@ -300,7 +300,7 @@ static struct dnode **dnalloc(int num)
 	if (num < 1)
 		return (NULL);
 
-	p = (struct dnode **) xcalloc((size_t) num, (size_t) (sizeof(struct dnode *)));
+	p = (struct dnode **) xzalloc(num * sizeof(struct dnode *));
 	return (p);
 }