When compiling libcurl with UNICODE defined and using unicode characters
in username.

Enabling test2017 to test2022.

Currently it is unknown if there is any version of clang that
actually supports -Wstrict-aliasing. What is known is that there
are several that don't support it.

With this commit, checks done in previous test2017 are now done in test2018.

Whole range test2017 to test2022 DISABLED until configure is capable of
requiring a new-enough metalink library.

Don't try these without mentioned check in place!

Print "parsing (...) OK" only when no warnings are generated.  If
no file is found in Metalink, treat it FAILED.

If no digest is provided, print WARNING in parse_metalink().
Also print validating FAILED after download.

These changes make tests 2012 to 2016 pass.

Reported by Tatsuhiro Tsujikawa

http://curl.haxx.se/mail/lib-2012-06/0371.html

Allow NTLM authentication when building using SecureTransport (Darwin) for SSL.

This uses CommonCrypto, a cryptography library that ships with all versions of
iOS and Mac OS X. It's like OpenSSL's libcrypto, except that it's missing a few
less-common cyphers and doesn't have a big number data structure.

Before commit 2dded8fe (dec 2010) there was logic that used
RAND_screen() at times and now I remove the leftover #ifdef check for
it.

The seeding code that uses Curl_FormBoundary() in ossl_seed() is dubious
to keep since it hardly increases randomness but I fear I'll break
something if I remove it now...

- Renamed st_ function prefix to darwinssl_
- Renamed Curl_st_ function prefix to Curl_darwinssl_
- Moved the duplicated ssl_connect_done out of the #ifdef in lib/urldata.h
- Fixed a teensy little bug that made non-blocking connection attempts block
- Made it so that it builds cleanly against the iOS 5.1 SDK

Fixed warning: dereferencing pointer does break strict-aliasing rules
by using a union inside the struct Curl_sockaddr_storage declaration.

curl_ntlm_msgs.c would previously use an #ifdef maze and direct
SSL-library calls instead of using the SSL layer we have for this
purpose.