Change return value of getentropy() to int 0 for success. Maximum

buffersize is enforced strictly, this supplies sufficient entropy
payload to act as seed material.  Discourage general use of this
API, but lock down this function name as the go-to for userland
PRNG seeding.  Improve documentation.
ok miod matthew

src/include/unistd.h

@@ -1,4 +1,4 @@
-/*	$OpenBSD: unistd.h,v 1.87 2014/06/13 08:26:10 deraadt Exp $ */
+/*	$OpenBSD: unistd.h,v 1.88 2014/06/14 18:01:41 deraadt Exp $ */
 /*	$NetBSD: unistd.h,v 1.26.4.1 1996/05/28 02:31:51 mrg Exp $	*/
 
 /*-
@@ -538,7 +538,7 @@ void	 setusershell(void);
 int	 strtofflags(char **, u_int32_t *, u_int32_t *);
 int	 swapctl(int cmd, const void *arg, int misc);
 int	 syscall(int, ...);
-ssize_t	 getentropy(void *, size_t);
+int	 getentropy(void *, size_t);
 pid_t	 __tfork_thread(const struct __tfork *, size_t, void (*)(void *),
 	    void *);
 #endif /* __BSD_VISIBLE */