Uppity: option to disallow SSH-1 compression.

With this and the ciphers, I think we've now got the full range of
SSH-1 config options (such as they are) that correspond to varying the
KEXINIT strings in SSH-2.

sshserver.h

@@ -15,6 +15,7 @@ struct SshServerConfig {
     bool exit_signal_numeric;          /* mimic an old server bug */
 
     unsigned long ssh1_cipher_mask;
+    bool ssh1_allow_compression;
 };
 
 Plug *ssh_server_plug(