Howard Chu brought the bulk work of this patch that properly
moves out the sending and recving of data to the parts of the
code that are properly responsible for the various ways of doing
so.
Daniel Stenberg assisted with polishing a few bits and fixed some
minor flaws in the original patch.
Another upside of this patch is that we now abuse CURLcodes less
with the "magic" -1 return codes and instead use CURLE_AGAIN more
consistently.
the global timeout if set. Also, as was reported in the bug report #2956437
by Ryan Chan, the time stamp to use as basis for the per command timeout was
not set properly in the DONE phase for FTP (and not for SMTP) so I fixed
that just now. This was a regression compared to 7.19.7 due to the
conversion of FTP code over to the generic pingpong concepts.
http://curl.haxx.se/bug/view.cgi?id=2956437
