AF_INET6 may not exist then

Patched-by: Iida Yosiaki
Bug: http://curl.haxx.se/bug/view.cgi?id=1322

When the requested authentication bitmask includes NTLM, we cannot
re-use a connection for another username/password as we then risk
re-using NTLM (connection-based auth).

This has the unfortunate downside that if you include NTLM as a possible
auth, you cannot re-use connections for other usernames/passwords even
if NTLM doesn't end up the auth type used.

Reported-by: Paras S
Patched-by: Paras S
Bug: http://curl.haxx.se/mail/lib-2014-01/0046.html

The Windows console version of stunnel is called "tstunnel", while
running "stunnel" on Windows spawns a new console window which
cannot be handled by the testsuite.

Previously LIST always returned a fixed hardcoded list that the ftp
server code knew about, mostly since the server didn't get any test case
number in the LIST scenario. Starting now, doing a CWD to a directory
named test-[number] will make the test server remember that number and
consider it a test case so that a subsequent LIST command will send the
<data> section of that test case back.

It allows LIST tests to be made more similar to how all other tests
work.

Test 100 was updated to provide its own directory listing.

Replaced the use of CURLOPT_USERPWD for the preferred CURLOPT_USERNAME
and CURLOPT_PASSWORD options and used the same username and password for
all email examples which is the same as that used in the test suite.

This is desired to support stunnel installations on Windows.