Remove internal separated behavior of the easy vs multi intercace.
curl_easy_perform() is now using the multi interface itself.
Several minor multi interface quirks and bugs have been fixed in the
process.
Much help with debugging this has been provided by: Yang Tse
1- Two new error codes are introduced.
CURLE_FTP_ACCEPT_FAILED to be set whenever ACCEPTing fails because of
FTP server connected.
CURLE_FTP_ACCEPT_TIMEOUT to be set whenever ACCEPTing timeouts.
Neither of these errors are considered fatal and control connection
remains OK because it could just be a firewall blocking server to
connect to the client.
2- One new setopt option was introduced.
CURLOPT_ACCEPTTIMEOUT_MS
It sets the maximum amount of time FTP client is going to wait for a
server to connect. Internal default accept timeout is 60 seconds.
The protocol parts for these tests do not include QUIT simply because
the error is CURLE_OPERATION_TIMEDOUT (28) which is a generic timeout
error without specificly saying for which connection it concerns, and
for timeouts libcurl marks the control channel as "invalid". As this
test case times out for the data connection it could still use the
control channel.
591 -> FTP multi PORT and 425 on upload
592 -> FTP multi PORT and 421 on upload
593 -> FTP multi PORT upload, no data conn and no transient neg. reply
594 -> FTP multi PORT upload, no data conn and no positive prelim. reply
1206 -> FTP PORT and 425 on download
1207 -> FTP PORT and 421 on download
1208 -> FTP PORT download, no data conn and no transient negative reply
1209 -> FTP PORT download, no data conn and no positive preliminary reply
