s/key: ask password during connection

[kokamomi]

hi, in order to use s/key authentication it would help
tremendously to have the password dialog not before the
connection attempt, but rather when the server prompts
for it. this is because when logging in as user:skey
you will get a hint from the server on how to generate
your one time password locally, thus not requiring you
to remember your s/key id and what sequence number
you're currently at, or alternatively having a
pre-generated one time password at disposal.

[Tim Kosse]

Will be supported in FileZilla 3. Release date still unknown.