Remove Kerberos 4 support

Signed-off-by: Sebastian Ramacher <sebastian+dev@ramacher.at>
Remove Kerberos 4 from the documentation

Signed-off-by: Sebastian Ramacher <sebastian+dev@ramacher.at>
Update translation files

Signed-off-by: Sebastian Ramacher <sebastian+dev@ramacher.at>
Remove declarations of unused functions

Signed-off-by: Sebastian Ramacher <sebastian+dev@ramacher.at>
Update REAMDE and INSTALL

Signed-off-by: Sebastian Ramacher <sebastian+dev@ramacher.at>
Handle va_list in ftp_print_cmd correctly

Signed-off-by: Sebastian Ramacher <sebastian+dev@ramacher.at>