need strsep() prototype for 64bit systems

http://bugs.gentoo.org/258795

--- a/auth2-pubkey.c
+++ b/auth2-pubkey.c
@@ -54,6 +54,7 @@
 #endif
 #include "monitor_wrap.h"
 #include "ssh-x509.h"
+#include <string.h>
 #include "misc.h"
 
 /* import */