Give BPPs a Frontend, so they can do their own logging.

The sshverstring quasi-frontend is passed a Frontend pointer at setup
time, so that it can generate Event Log entries containing the local
and remote version strings and the results of remote bug detection.

I'm promoting that field of sshverstring to a field of the public BPP
structure, so now all BPPs have the right to talk directly to the
frontend if they want to. This means I can move all the log messages
of the form 'Initialised so-and-so cipher/MAC/compression' down into
the BPPs themselves, where they can live exactly alongside the actual
initialisation of those primitives.

It also means BPPs will be able to log interesting things they detect
at any point in the packet stream, which is about to come in useful
for another purpose.

ssh1login.c

@@ -406,7 +406,6 @@ static void ssh1_login_process_queue(PacketProtocolLayer *ppl)
             (s->cipher_type == SSH_CIPHER_BLOWFISH ? &ssh1_blowfish :
              s->cipher_type == SSH_CIPHER_DES ? &ssh1_des : &ssh1_3des);
         ssh1_bpp_new_cipher(s->ppl.bpp, cipher, s->session_key);
-        ppl_logevent(("Initialised %s encryption", cipher->text_name));
     }
 
     if (s->servkey.modulus) {
@@ -1114,7 +1113,6 @@ static void ssh1_login_process_queue(PacketProtocolLayer *ppl)
              * easiest way to avoid race conditions if other packets
              * cross in transit.)
              */
-            ppl_logevent(("Started zlib (RFC1950) compression"));
 	} else if (pktin->type == SSH1_SMSG_FAILURE) {
             ppl_logevent(("Server refused to enable compression"));
 	    ppl_printf(("Server refused to compress\r\n"));