... when we are not asked to use a certificate from file

- unknown protocols probably won't send more headers (e.g. WebSocket)
- improved comments and moved them to the correct case statements

Closes #899

synced with OpenSSL git master commit cc06906707

... instead of relying on the pkg-config autoconf macros to be present.

Fixes #972 (again...)

.. also remove same from scp

When we're uploading using FTP and the server issues a tiny pause
between opening the connection to the client's secondary socket, the
client's initial poll() times out, which leads to second poll() which
does not wait for POLLIN on the secondary socket. So that poll() also
has to time out, creating a long (200ms) pause.

This patch adds the correct flag to the secondary socket, making the
second poll() correctly wait for the connection there too.

Signed-off-by: Ales Novak <alnovak@suse.cz>

Closes #978

With commit c2f9b78a we added a new dependency on pkg-config for
developers which may be unwanted. This change make the configure script
still work as before if pkg-config isn't installed, it'll just use the
old zlib detection logic without pkg-config.

Reported-by: Marc Hörsken

Fixes #972

This reverts commit 9cb1059f.

As discussed in #835 SOCKS5 supports IPv6 proxies and destinations.

Closes #820

Only choose the GSSAPI authentication mechanism when the user name
contains a Windows domain name or the user is a valid UPN.

Fixes #718

Completing commit 00417fd6 and 2708d425.

From commit 2708d425.

Instead of displaying the requested hostname the one returned
by the SOCKS5 proxy server is used in case of connection error.
The requested hostname is displayed earlier in the connection sequence.

The upper-value of the port is moved to a temporary variable and
replaced with a 0-byte to make sure the hostname is 0-terminated.

As of 7.25.0 and commit 54300072.

Replace custom string formatting with Curl_printable_address.
Add additional debug and error output in case of failures.

Calling sscanf is not required since the raw IPv4 address is
available and the protocol can be detected using ai_family.

Made by Visual Studio's auto-correct feature and missed by me in my own
code reviews!

Hooked up the HTTP authentication layer to query the new 'is mechanism
supported' functions when deciding what mechanism to use.

As per commit 00417fd6 existing functionality is maintained for now.

Hooked up the SASL authentication layer to query the new 'is mechanism
supported' functions when deciding what mechanism to use.

For now existing functionality is maintained.

As Windows SSPI authentication calls fail when a particular mechanism
isn't available, introduced these functions for DIGEST, NTLM, Kerberos 5
and Negotiate to allow both HTTP and SASL authentication the opportunity
to query support for a supported mechanism before selecting it.

For now each function returns TRUE to maintain compatability with the
existing code when called.

...and removed some old ones

RFC7512 provides a standard method to reference certificates in PKCS#11
tokens, by means of a URI starting 'pkcs11:'.

We're working on fixing various applications so that whenever they would
have been able to use certificates from a file, users can simply insert
a PKCS#11 URI instead and expect it to work. This expectation is now a
part of the Fedora packaging guidelines, for example.

This doesn't work with cURL because of the way that the colon is used
to separate the certificate argument from the passphrase. So instead of

   curl -E 'pkcs11:manufacturer=piv_II;id=%01' …

I instead need to invoke cURL with the colon escaped, like this:

   curl -E 'pkcs11\:manufacturer=piv_II;id=%01' …

This is suboptimal because we want *consistency* — the URI should be
usable in place of a filename anywhere, without having strange
differences for different applications.

This patch therefore disables the processing in parse_cert_parameter()
when the string starts with 'pkcs11:'. It means you can't pass a
passphrase with an unescaped PKCS#11 URI, but there's no need to do so
because RFC7512 allows a PIN to be given as a 'pin-value' attribute in
the URI itself.

Also, if users are already using RFC7512 URIs with the colon escaped as
in the above example — even providing a passphrase for cURL to handling
instead of using a pin-value attribute, that will continue to work
because their string will start 'pkcs11\:' and won't match the check.

What *does* break with this patch is the extremely unlikely case that a
user has a file which is in the local directory and literally named
just "pkcs11", and they have a passphrase on it. If that ever happened,
the user would need to refer to it as './pkcs11:<passphrase>' instead.

This allows for better memmory debugging and torture tests.

This fixes tests that were added after 113f04e6 as the tests would
fail otherwise.

We bring back "Proxy-Connection: Keep-Alive" now unconditionally to fix
regressions with old and stupid proxies, but we could possibly switch to
using it only for CONNECT or only for NTLM in a future if we want to
gradually reduce it.

Fixes #954

Reported-by: János Fekete

This reverts commit 113f04e6.

Follow-up to a96319eb (document the new behavior)