This makes the tests succeed when using --disable-proxy.

Closes https://github.com/curl/curl/pull/4488

When using basic-auth, connections and proxy connections
can be re-used with different Authorization headers since
it does not authenticate the connection (like NTLM does).

For instance, the below command should re-use the proxy
connection, but it currently doesn't:
curl -v -U alice:a -x http://localhost:8181 http://localhost/
  --next -U bob:b -x http://localhost:8181 http://localhost/

This is a regression since refactoring of ConnectionExists()
as part of: cb4e2be7c6d42ca0780f8e0a747cecf9ba45f151

Fix the above by removing the username and password compare
when re-using proxy connection at proxy_info_matches().

However, this fix brings back another bug would make curl
to re-print the old proxy-authorization header of previous
proxy basic-auth connection because it wasn't cleared.

For instance, in the below command the second request should
fail if the proxy requires authentication, but would succeed
after the above fix (and before aforementioned commit):
curl -v -U alice:a -x http://localhost:8181 http://localhost/
  --next -x http://localhost:8181 http://localhost/

Fix this by clearing conn->allocptr.proxyuserpwd after use
unconditionally, same as we do for conn->allocptr.userpwd.

Also fix test 540 to not expect digest auth header to be
resent when connection is reused.

Signed-off-by: Isaac Boukris <iboukris@gmail.com>

Closes https://github.com/curl/curl/pull/1350

This reverts commit 113f04e664b16b944e64498a73a4dab990fe9a68.

RFC 7230 says we should stop. Firefox already stopped.

Bug: https://github.com/curl/curl/issues/633
Reported-By: Brad Fitzpatrick

Closes #633

...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.

Instead of using haxx.se as a fixed magic host name in lots of tests,
this is a first step to move toward the generic example.com host
instead.

  used. It has been used since forever but it was never a good idea to use
  unless explicitly asked for.