There was a merge collision in multi.c's multi_runsingle() function at the
point where we have a local patch concerning bug 1420. The upstream change was
to change a Curl_done() call to multi_done(). Our patch called Curl_done() in
each clause of an 'if' statement; we changed both to multi_done(). However,
our patch also had a Curl_posttransfer() call; we overzealously changed that
to multi_posttransfer() too. But there is no such function. Change back to
Curl_posttransfer().