Add a NODELAY option

Add a new option SSH_OPTIONS_NODELAY to enable or disable the
Nagle Algorithm (TCP_NODELAY) on the session socket.

Improved performance can be achieved for some applications like
sftp servers by enabling SSH_OPTIONS_NODELAY as typically, the
next request won't arrive until the server replies, which are
typically small writes.

Signed-off-by: Alberto Aguirre <albaguirre@gmail.com>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>

src/session.c

@@ -107,6 +107,7 @@ ssh_session ssh_new(void) {
     session->opts.fd = -1;
     session->opts.ssh2 = 1;
     session->opts.compressionlevel=7;
+    session->opts.nodelay = 0;
 #ifdef WITH_SSH1
     session->opts.ssh1 = 1;
 #else