For consistency with other USE_WIN32_ defines as well as the
USE_OPENLDAP define.

Use a dynamicly allocated buffer for the temporary SPN variable similar
to how the SASL GSS-API code does, rather than using a fixed buffer of
2048 characters.

Carrying on from commit 037cd0d9, removed the following unimplemented
instances of curlssl_close_all():

Curl_axtls_close_all()
Curl_darwinssl_close_all()
Curl_cyassl_close_all()
Curl_gskit_close_all()
Curl_gtls_close_all()
Curl_nss_close_all()
Curl_polarssl_close_all()

Slight code cleanup as the SSL backend #define is mixed up with the API
function setup.

Fixed the following warning and error from commit 3af90a6e when SSL
is not being used:

url.c:2004: warning C4013: 'Curl_ssl_cert_status_request' undefined;
            assuming extern returning int

error LNK2019: unresolved external symbol Curl_ssl_cert_status_request
               referenced in function Curl_setopt

Use the same variable name as other areas of SSPI code.

Use the SECURITY_STATUS typedef rather than a unsigned long for the
QuerySecurityPackageInfo() return and rename the variable as per other
areas of SSPI code.

Missed Curl_read64_be() in commit bb12d444 :(

This enables the CURLOPT_SSL_VERIFYSTATUS functionality.

Also known as "status_request" or OCSP stapling, defined in RFC6066 section 8.

This requires NSS 3.15 or higher.

Also known as "status_request" or OCSP stapling, defined in RFC6066 section 8.

This requires GnuTLS 3.1.3 or higher to build, however it's recommended to use
at least GnuTLS 3.3.11 since previous versions had a bug that caused the OCSP
response verfication to fail even on valid responses.

This option can be used to enable/disable certificate status verification using
the "Certificate Status Request" TLS extension defined in RFC6066 section 8.

This also adds the CURLE_SSL_INVALIDCERTSTATUS error, to be used when the
certificate status verification fails, and the Curl_ssl_cert_status_request()
function, used to check whether the SSL backend supports the status_request
extension.

Bug: http://curl.haxx.se/mail/lib-2015-01/0094.html
Reported-by: John E. Malmberg

Reported-by: Mohammad AlSaleh
Bug: http://curl.haxx.se/mail/lib-2015-01/0065.html

If the session is still used by active SSL/TLS connections, it
cannot be closed yet. Thus we mark the session as not being cached
any longer so that the reference counting mechanism in
Curl_schannel_shutdown is used to close and free the session.

Reported-by: Jean-Francois Durand

add -m64 CFLAGS when targeting mingw64, add -m32/-m64 to LDFLAGS

mingw build: allow to pass custom CFLAGS

Better code reuse and consistency in calls to gss_import_name().