Include openssl compatibility.

Patch from rosenp at gmail.com via openssh-unix-dev.
diff --git a/ssh_api.c b/ssh_api.c
index c84b4e7..e727c0d 100644
--- a/ssh_api.c
+++ b/ssh_api.c
@@ -29,6 +29,8 @@
 #include "ssherr.h"
 #include "sshbuf.h"
 
+#include "openbsd-compat/openssl-compat.h"
+
 #include <string.h>
 
 int	_ssh_exchange_banner(struct ssh *);