Decide on a position for ChaCha20-Poly1305.

Previously, due to confusion, it was placed either at the end of the
list or at the start, depending on whether the user had any saved
configuration at all. Now we get to choose a sensible place for it in
the list, and for the moment I think second place behind AES is
reasonable.

settings.c

@@ -10,8 +10,8 @@
 
 /* The cipher order given here is the default order. */
 static const struct keyvalwhere ciphernames[] = {
-    { "chacha20",   CIPHER_CHACHA20,        -1, -1 },
     { "aes",        CIPHER_AES,             -1, -1 },
+    { "chacha20",   CIPHER_CHACHA20,        CIPHER_AES, +1 },
     { "blowfish",   CIPHER_BLOWFISH,        -1, -1 },
     { "3des",       CIPHER_3DES,            -1, -1 },
     { "WARN",       CIPHER_WARN,            -1, -1 },