messages: Use ssh_publickey_state_e instead of char

Use the enum type instead of char in the ssh_auth_request struct

Fixes T194

Signed-off-by: Anderson Toshiyuki Sasaki <ansasaki@redhat.com>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
(cherry picked from commit 39f6ba2dc9)

include/libssh/messages.h

@@ -28,7 +28,7 @@ struct ssh_auth_request {
     int method;
     char *password;
     struct ssh_key_struct *pubkey;
-    char signature_state;
+    enum ssh_publickey_state_e signature_state;
     char kbdint_response;
 };