Wrap <unistd.h> so that internal calls go direct and they're all weak symbols

Delete unused 'fd' argument from internal function oldttyname()

src/lib/libc/crypt/crypt.c

@@ -1,7 +1,8 @@
-/*	$OpenBSD: crypt.c,v 1.30 2015/07/18 01:18:50 jeremy Exp $	*/
+/*	$OpenBSD: crypt.c,v 1.31 2015/09/12 14:56:50 guenther Exp $	*/
 
 #include <errno.h>
 #include <pwd.h>
+#include <unistd.h>
 
 char *
 crypt(const char *key, const char *setting)
@@ -18,3 +19,4 @@ crypt(const char *key, const char *setting)
 	errno = EINVAL;
 	return (NULL);
 }
+DEF_WEAK(crypt);

src/lib/libc/crypt/cryptutil.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: cryptutil.c,v 1.10 2015/07/23 22:19:03 tedu Exp $ */
+/* $OpenBSD: cryptutil.c,v 1.11 2015/09/12 14:56:50 guenther Exp $ */
 /*
  * Copyright (c) 2014 Ted Unangst <tedu@openbsd.org>
  *
@@ -50,6 +50,7 @@ fail:
 	errno = EACCES;
 	return -1;
 }
+DEF_WEAK(crypt_checkpass);
 
 int
 crypt_newhash(const char *pass, const char *pref, char *hash, size_t hashlen)
@@ -95,3 +96,4 @@ crypt_newhash(const char *pass, const char *pref, char *hash, size_t hashlen)
 err:
 	return rv;
 }
+DEF_WEAK(crypt_newhash);