Patch for telnet / telnetd to avoid crashes when used with MS kdc and PAC field

[Markus Moeller]

I intoduced a TELNET_BUFSIZ to increase several buffers to be able to handle tickets received by a MS kdc and a big pac field (e.g. more than 200 group memberships). I also increased the FTP_BUFSIZ fro the same reason.
 
Regards
Markus