First off the timeout for accepting a server connect back must of course
respect a global timeout. Then the timeleft function is only used by ftp
code so it was moved to ftp.c and made static.
"wait_data_conn" was added to the connectionbits in commit c834213ad5 for
handling active FTP connections but as it is purely FTP specific and now
only ever accessed by ftp.c I moved it into the FTP connection struct.
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.
command is a special "hack" used by the drftpd server, but even though it is
a custom extension I've deemed it fine to add to libcurl since this server
seems to survive and people keep using it and want libcurl to support
it. The new libcurl option is named CURLOPT_FTP_USE_PRET, and it is also
usable from the curl tool with --ftp-pret. Using this option on a server
that doesn't support this command will make libcurl fail.
doing an FTP transfer is removed from a multi handle before completion. The
fix also fixed the "alive counter" to be correct on "premature removal" for
all protocols.
