Change vtable defs to use C99 designated initialisers.

This is a sweeping change applied across the whole code base by a spot
of Emacs Lisp. Now, everywhere I declare a vtable filled with function
pointers (and the occasional const data member), all the members of
the vtable structure are initialised by name using the '.fieldname =
value' syntax introduced in C99.

We were already using this syntax for a handful of things in the new
key-generation progress report system, so it's not new to the code
base as a whole.

The advantage is that now, when a vtable only declares a subset of the
available fields, I can initialise the rest to NULL or zero just by
leaving them out. This is most dramatic in a couple of the outlying
vtables in things like psocks (which has a ConnectionLayerVtable
containing only one non-NULL method), but less dramatically, it means
that the new 'flags' field in BackendVtable can be completely left out
of every backend definition except for the SUPDUP one which defines it
to a nonzero value. Similarly, the test_for_upstream method only used
by SSH doesn't have to be mentioned in the rest of the backends;
network Plugs for listening sockets don't have to explicitly null out
'receive' and 'sent', and vice versa for 'accepting', and so on.

While I'm at it, I've normalised the declarations so they don't use
the unnecessarily verbose 'struct' keyword. Also a handful of them
weren't const; now they are.

sshdes.c

@@ -683,16 +683,34 @@ static void des_cbc_decrypt(ssh_cipher *ciph, void *vdata, int len)
 }
 
 const ssh_cipheralg ssh_des = {
-    des_cbc_new, des_cbc_free, des_cbc_setiv, des_cbc_setkey,
-    des_cbc_encrypt, des_cbc_decrypt, NULL, NULL, "des-cbc",
-    8, 56, 8, SSH_CIPHER_IS_CBC, "single-DES CBC", NULL
+    .new = des_cbc_new,
+    .free = des_cbc_free,
+    .setiv = des_cbc_setiv,
+    .setkey = des_cbc_setkey,
+    .encrypt = des_cbc_encrypt,
+    .decrypt = des_cbc_decrypt,
+    .ssh2_id = "des-cbc",
+    .blksize = 8,
+    .real_keybits = 56,
+    .padded_keybytes = 8,
+    .flags = SSH_CIPHER_IS_CBC,
+    .text_name = "single-DES CBC",
 };
 
 const ssh_cipheralg ssh_des_sshcom_ssh2 = {
     /* Same as ssh_des_cbc, but with a different SSH-2 ID */
-    des_cbc_new, des_cbc_free, des_cbc_setiv, des_cbc_setkey,
-    des_cbc_encrypt, des_cbc_decrypt, NULL, NULL, "des-cbc@ssh.com",
-    8, 56, 8, SSH_CIPHER_IS_CBC, "single-DES CBC", NULL
+    .new = des_cbc_new,
+    .free = des_cbc_free,
+    .setiv = des_cbc_setiv,
+    .setkey = des_cbc_setkey,
+    .encrypt = des_cbc_encrypt,
+    .decrypt = des_cbc_decrypt,
+    .ssh2_id = "des-cbc@ssh.com",
+    .blksize = 8,
+    .real_keybits = 56,
+    .padded_keybytes = 8,
+    .flags = SSH_CIPHER_IS_CBC,
+    .text_name = "single-DES CBC",
 };
 
 static const ssh_cipheralg *const des_list[] = {
@@ -784,9 +802,18 @@ static void des3_cbc1_cbc_decrypt(ssh_cipher *ciph, void *vdata, int len)
 }
 
 const ssh_cipheralg ssh_3des_ssh2 = {
-    des3_cbc1_new, des3_cbc1_free, des3_cbc1_setiv, des3_cbc1_setkey,
-    des3_cbc1_cbc_encrypt, des3_cbc1_cbc_decrypt, NULL, NULL, "3des-cbc",
-    8, 168, 24, SSH_CIPHER_IS_CBC, "triple-DES CBC", NULL
+    .new = des3_cbc1_new,
+    .free = des3_cbc1_free,
+    .setiv = des3_cbc1_setiv,
+    .setkey = des3_cbc1_setkey,
+    .encrypt = des3_cbc1_cbc_encrypt,
+    .decrypt = des3_cbc1_cbc_decrypt,
+    .ssh2_id = "3des-cbc",
+    .blksize = 8,
+    .real_keybits = 168,
+    .padded_keybytes = 24,
+    .flags = SSH_CIPHER_IS_CBC,
+    .text_name = "triple-DES CBC",
 };
 
 /* ----------------------------------------------------------------------
@@ -872,9 +899,18 @@ static void des3_sdctr_encrypt_decrypt(ssh_cipher *ciph, void *vdata, int len)
 }
 
 const ssh_cipheralg ssh_3des_ssh2_ctr = {
-    des3_sdctr_new, des3_sdctr_free, des3_sdctr_setiv, des3_sdctr_setkey,
-    des3_sdctr_encrypt_decrypt, des3_sdctr_encrypt_decrypt,
-    NULL, NULL, "3des-ctr", 8, 168, 24, 0, "triple-DES SDCTR", NULL
+    .new = des3_sdctr_new,
+    .free = des3_sdctr_free,
+    .setiv = des3_sdctr_setiv,
+    .setkey = des3_sdctr_setkey,
+    .encrypt = des3_sdctr_encrypt_decrypt,
+    .decrypt = des3_sdctr_encrypt_decrypt,
+    .ssh2_id = "3des-ctr",
+    .blksize = 8,
+    .real_keybits = 168,
+    .padded_keybytes = 24,
+    .flags = 0,
+    .text_name = "triple-DES SDCTR",
 };
 
 static const ssh_cipheralg *const des3_list[] = {
@@ -998,7 +1034,15 @@ static void des3_cbc3_cbc_decrypt(ssh_cipher *ciph, void *vdata, int len)
 }
 
 const ssh_cipheralg ssh_3des_ssh1 = {
-    des3_cbc3_new, des3_cbc3_free, des3_cbc3_setiv, des3_cbc3_setkey,
-    des3_cbc3_cbc_encrypt, des3_cbc3_cbc_decrypt, NULL, NULL, NULL,
-    8, 168, 24, SSH_CIPHER_IS_CBC, "triple-DES inner-CBC", NULL
+    .new = des3_cbc3_new,
+    .free = des3_cbc3_free,
+    .setiv = des3_cbc3_setiv,
+    .setkey = des3_cbc3_setkey,
+    .encrypt = des3_cbc3_cbc_encrypt,
+    .decrypt = des3_cbc3_cbc_decrypt,
+    .blksize = 8,
+    .real_keybits = 168,
+    .padded_keybytes = 24,
+    .flags = SSH_CIPHER_IS_CBC,
+    .text_name = "triple-DES inner-CBC",
 };