Treat STAT return code 200 (command ok) as valid result

we currently only check 213 (file exists) 150 (file status ok) and 211 (system ok).

FTC-959 ( http://www.faqs.org/rfcs/rfc959.html ) defines the following return values for STAT:

STAT
211, 212, 213
450
500, 501, 502, 421, 530

This doesnt contain the 200 value, but command ok is defined as being returned in case the server doesnt have more info to pass. This happened with a fairly recent ftp server. I'm also curious why we dont detect 212 but intead use 150 as ok indicator.