Rearranged code and changed Curl_readwrite_init() and Curl_pre_readwrite() into

do_init() and do_complete() which now are called first and last in the DO
function. It simplified the flow in multi.c and the functions got more
sensible names!

lib/file.c

@@ -378,7 +378,6 @@ static CURLcode Curl_file(struct connectdata *conn, bool *done)
 
   *done = TRUE; /* unconditionally */
 
-  Curl_readwrite_init(conn);
   Curl_initinfo(data);
   Curl_pgrsStartNow(data);