Pull in <time.h> for clock_gettime()

ok deraadt@

src/lib/libc/crypt/bcrypt.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: bcrypt.c,v 1.56 2016/06/26 21:04:08 tedu Exp $	*/
+/*	$OpenBSD: bcrypt.c,v 1.57 2016/08/26 08:25:02 guenther Exp $	*/
 
 /*
  * Copyright (c) 2014 Ted Unangst <tedu@openbsd.org>
@@ -39,6 +39,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <time.h>
 
 /* This implementation is adaptable to current computing power.
  * You can have up to 2^31 rounds which should be enough for some