Store default port number in each back end

[originally from svn r669]

putty.h

@@ -115,6 +115,7 @@ typedef struct {
     void (*special) (Telnet_Special code);
     SOCKET (*socket) (void);
     int (*sendok) (void);
+    int default_port;
 } Backend;
 
 GLOBAL Backend *back;

raw.c

@@ -243,5 +243,6 @@ Backend raw_backend = {
     raw_size,
     raw_special,
     raw_socket,
-    raw_sendok
+    raw_sendok,
+    1
 };

ssh.c

@@ -2627,5 +2627,6 @@ Backend ssh_backend = {
     ssh_size,
     ssh_special,
     ssh_socket,
-    ssh_sendok
+    ssh_sendok,
+    22
 };

telnet.c

@@ -761,5 +761,6 @@ Backend telnet_backend = {
     telnet_size,
     telnet_special,
     telnet_socket,
-    telnet_sendok
+    telnet_sendok,
+    23
 };