This is done by making sure each individual transfer is first added to a
linked list as then they can be performed serially, or at will, in
parallel.
Closes#3804
...after the method line:
"Since the Host field-value is critical information for handling a
request, a user agent SHOULD generate Host as the first header field
following the request-line." / RFC 7230 section 5.4
Additionally, this will also make libcurl ignore multiple specified
custom Host: headers and only use the first one. Test 1121 has been
updated accordingly
Bug: http://curl.haxx.se/bug/view.cgi?id=1491
Reported-by: Rainer Canavan
Added !SSPI to the features list of the HTTP digest tests, as SSPI
based builds now use the Windows SSPI messaging API rather than the
internal functions, and we can't control the random numbers that get
used as part of the digest.
