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>

include/libssh/libssh.h

@@ -355,7 +355,8 @@ enum ssh_options_e {
   SSH_OPTIONS_PUBKEY_AUTH,
   SSH_OPTIONS_KBDINT_AUTH,
   SSH_OPTIONS_GSSAPI_AUTH,
-  SSH_OPTIONS_GLOBAL_KNOWNHOSTS
+  SSH_OPTIONS_GLOBAL_KNOWNHOSTS,
+  SSH_OPTIONS_NODELAY,
 };
 
 enum {

include/libssh/session.h

@@ -205,6 +205,7 @@ struct ssh_session_struct {
         char *gss_client_identity;
         int gss_delegate_creds;
         int flags;
+        int nodelay;
     } opts;
     /* counters */
     ssh_counter socket_counter;